细菌如何进化出旋转马达 | 迈克尔·曼森

就像大肠杆菌一样，

And just like with E.

大肠杆菌朝一个方向旋转时是平滑游动，朝另一个方向旋转时则是翻滚。

Coli, one direction of spitting was smooth swimming, and the other direction of spitting was tumbling.

之所以会这样，是因为鞭毛是左旋螺旋结构，如果逆时针旋转，它们会形成整齐的束。

And the reason that happens is because the flagella are left handed helices, and if you turn them counterclockwise, they form a nice bundle.

如果开始顺时针旋转，那束鞭毛就会散开，全都散开，然后四处乱摆。

If you start turning them clockwise, that bundle flies apart, all the it'll go off and it just flails around.

对吧？

Right?

所以你的意思是，一束鞭毛，如果朝一个方向转，它们会一起旋转。

So meaning like a bundle of flagella, which all, if you're turning them one way, they all kind of spin together.

对。

Yeah.

如果把它们分开，那它们就散开了。

If you separate them, then they Flies apart.

它们在旋转，朝不同方向推进。

They're spinning, they're pushing in different directions.

对。

Yeah.

对。

Yeah.

这就是导致翻滚和重新定向的原因。

And that's what causes the tumble, causes the reorientation.

它有没有选择去哪里，还是随机的？不。

Is there any choice of where it goes, or it's a random No.

只是随机的。

It's just random.

只是朝某个新的随机方向，它们又开始逆时针旋转鞭毛，重新形成束，然后朝那个新方向游走。

It's just it's just in some new random direction, they start turning the flagellar counterclockwise again, the bundle reforms, and they swim off in that new direction.

所以它只是走走停停。

So it's only like stop and go.

就只有这样。

That's the only

停，走。

Stop, go.

随机。

Random.

好的。

Okay.

咕噜。

Gulp.

对。

Yeah.

霍华德·伯格发明了一种显微镜，证明了这一点。

And and Howard Berg developed a microscope that showed that.

他发明的显微镜能通过移动载物台，让细菌在显微镜下始终保持对焦。

He developed a microscope that could keep a bacterium in a microscope in focus, right, by moving the stage to keep it in focus in the microscope.

如果你记录下载物台的动作，对吧，就能知道细菌的运动轨迹。

And if you record the motions of the stage, right, that tells you the path of the bacterium.

这就是他实现自动追踪的方法，也是他用来证明细菌会奔跑和撞击的方式。

And that's how he the automatic tracking, because that's how he showed that they ran and pummeled.

我是说，伯格是个天才般的仪器专家，绝对是这方面的天才。

I mean, Berg was an instrumental genius, an absolute instrumental genius.

在科罗拉多大学时，有一位老派的德国物理学家兼机械师负责管理车间，而霍华德·伯格是唯一能用上那些精密设备的人。

He at Colorado, there was an old German physicist, old German machinist that ran the machine shop, and Howard Berg was the only guy that got to use all of the sophisticated equipment.

其他人，不管是学生还是老师，都有自己的小地方放些简单设备，但霍华德能进来用那些最精密的设备，因为他确实厉害，对吧？

Nobody else, students or faculty, could they had a separate little place where they could, you know, have simple equipment, but Howard got to come in and use the most sophisticated equipment because he was that good at it, right?

就连那位特别挑剔的德国机械师也得让霍华德使用。

And even the very particular German machinist had to let Howard Berg use.

这就是霍华德会做的事。

That's what Howard would do.

他最喜欢的事就是去车间开始搞点制作。

That's his favorite thing, was go to a machine shop and start building something.

那才是他真正喜欢做的事，而且他在这方面非常擅长。

That's what he really loved to do, and he was really good at it.

但是，是的，这些家伙是被拴住的。

But, yeah, so these guys are tethered.

对吧？

Right?

但是，对于大肠杆菌，

But so, with E.

首先是在大肠杆菌上展示的，

Coli, was shown first with E.

但链球菌也是如此，它们朝一个方向旋转，所以如果我们观察，如果鞭毛逆时针旋转，细胞就顺时针运动，对吧，如果你固定住鞭毛的话。

Coli, but it was true for the streptococci as well, they turn one direction, and that's so if we were looking at it, if the flagella would be turning counterclockwise, the cell is going clockwise, right, if you hold the flagellum still.

然后反转，鞭毛顺时针旋转，细胞就逆时针运动。

And then with a reverse, where the flagellum would be going clockwise, and the cell goes counterclockwise.

所以你可以证明这一点，而且你可以证明，如果加入一种吸引性化学物质，它们朝那个方向运动的时间会更长，对吧？

And so you could show that, and you could show that if you added an attractant chemical that they spent a longer time going in that direction, right?

而且你可以很容易地量化，只要观察它们朝那个方向运动的时间，直到它们适应信号为止。

And you could very easily quantify by just by looking at the time they did that until they adapted to the signal.

链球菌也会做同样的事情。

And with the streptococcus, they would do the same thing.

转一个方向，再转另一个方向，转一个方向，再转另一个方向。

Turn one way, turn the other way, turn one way, turn the other way.

所以我做的就是设置不同强度的质子动力势。

And so what I did was I set up different magnitudes of proton motive force.

这些细胞是饥饿状态的。

It had starved cells.

它们就那样被拴着，一动不动。

They were just sitting there tethered.

它们只是在那里摆动。

They'd just wiggle around.

然后你加入缬氨霉素，配合不同的外部钾浓度，对吧，这样就能得到不同大小的钾扩散电位，或者用不同的pH值，然后它们就开始旋转了。

And then you would add velinomycin with different external potassium concentrations, right, so you get a different magnitude of the of the potassium diffusion potential or with different pHs, and they'd start spinning.

明白吗？

Okay?

然后你记录它们旋转的速度，我听到的是一团数据。

And you record the speed at which they spin, and I heard this blob of data.

很难看出什么规律，让人很头疼。

It was very hard to see anything, and horrified.

所以你把数据画出来，看看这里到底发生了什么。

So you get off the pot, plot your data, see what's going really going on here.

结果发现，当你这么做的时候，虽然单个数据点看起来像散点图，但在不同的质子动力下，趋势非常明显。

And it turned out when you did that, even though the individual data just were like a scatter plot, that you got very clear trends at the different proton motive forces.

然后如果你根据细胞长度进行校正，因为造成所有散点的原因是小细胞比大细胞旋转得快得多。

And if you then correct it for the length of the cell, because what caused the diff all the scatter was that small cells turn much faster than large cells.

对吧？

Right?

因为事实证明，马达以恒定扭矩运转，这意味着它转动长细胞的速度会比转动小细胞慢得多。

Because it turns out that the motor operates at constant torque, which means it's gonna turn a long cell much slower than it turns a small cell.

所以我所有的数据分散都是因为这个，当我根据细胞长度进行校正后，它们形成了非常漂亮的图，对吧，线性关系图，显示质子动力势与速度的关系。

So all my scatter was due to that, and when I corrected for the length of the cells, they formed really nice plots, right, linear plots with proton motive force and speed.

这就是我们发表在《分子生物学杂志》上的那篇论文，证明了鞭毛旋转的能量学，即旋转速度与高负荷下的质子动力势直接成正比，至少在某个范围内是这样。

And that was our paper that we published in Journal of Molecular Biology showing that in fact, it's called the energetics of flagellar rotation, that there was direct The speed of rotation was directly proportional, at least at range, this high load.

这个马达真的在拼命工作，对吧？

This motor's really working hard, right?

那是个大装置。

It's a big set.

它在旋转那个

Is spinning the

对，是的，Minority在旋转那个小鞭毛，对吧？

whole Yeah, Minority is spinning the little flagellar, right?

它们每秒能转300圈。

And they go like 300 rotations per second.

这些家伙呢，你知道，每秒只转一两圈。

These guys are turning at, you know, one to a few rotations per second.

所以它们工作的状态并不是它们正常功能下的状态，但在那个范围内，它们以恒定扭矩运行。

So they're working at really not where they would normally be working in their in their normal function, but in that range, they're operating at constant torque.

是的。

Yes.

那么，下一个问题是，是什么改变了扭矩的方向？

Like, next question is, like, what switches the direction of the torque?

哦，

Oh,

你看，现在你触及到了

well, see, now you're getting to the

那是

That's a

事情的关键。

the crux of things.

所以那是一个关键点。

So that's one crux.

明白了。

I see.

这就是2026年那篇论文的关键所在。

That's the crux from the paper of of 2026.

对吧？

Right?

所以Arvin Samuel发表了两篇论文。

So Arvin Samuel published these two papers.

他的实验室发表了两篇论文。

His lab published these two papers.

其中一篇是2025年12月发表的，他展示了那些小小的定子单元——我们一会儿会讲到——会旋转。

One was the one in in December 2025 where he showed that these little stator units, which we'll talk about in a moment, rotate.

然后在2026年3月，他展示了信号分子——磷酸基团——单个分子结合到鞭毛马达上，就会导致它反转方向。

And then in '20, March 2026, he showed that a single molecule of the of the the signaling, molecule, key y phosphate, a single one of those binding to the flagellar motor cause it to reverse direction.

好的。

Okay.

那这又需要另外一整套东西来设置，才能搞清楚它是怎么运作的。

Now, that that will require another whole set of things to set up, how how that works.

但也许我们还是先专注于马达，好的，首先，就像我说的，要深入细节的话，我得先退一步。

But maybe to stick with the motor, okay, first, and as I say, to get into the details of Okay.

我得稍微往回讲一点。

I have to back up a little bit.

我们早就知道的是，你可以构建一个完整的鞭毛。

So what we knew, and we was known for a long time, was that you could make a complete flagellar.

就是说，如果你看你的图，对吧？

Mean, if you look at your picture, right?

你看这个，你可以把所有这些结构都做出来，对吧？

You if you look at this, you can make all of this, right, all of that structure.

但如果没有这些小东西，它就不会转。

If you don't have this, these little guys, it doesn't turn.

它就不工作。

It doesn't work.

对吧？

Right?

所以你需要这两种蛋白质。

So you need these two proteins.

那是怎么知道的？

How was that known?

我是说，人们当时在提纯……

I mean, people were purifying

哦，你可以通过突变把基因敲除，然后从……表达蛋白质。

Oh, you could show you could show you knock out the gene with mutations, and then you'd express the protein from a

植物。所有成分是什么时候被弄清楚的？其实很早。

plant What point were all the components known, like, even Quite early.

那是怎么拼凑起来的？

How did that get put together?

哦，日本有一个团队把整个事情搞清楚了。

Oh, there's a group in Japan that put that all through.

他们确实做了。你知道，你可以想象，大概有30种不同的蛋白质参与构建这个结构。

They did I mean, they're, as you can imagine, they're like, I don't know, 30 different proteins that go into making this structure.

这是一个非常复杂的结构，而且有一些非常了不起的地方，比如你必须把构建鞭毛所需的所有东西都运出去，它们得从中间穿过去，扩散出去。

It's a very complex structure, and it has some really incredible aspects to it, like you have to export everything that gets built on to make this flagellum, has to go out through the middle of it, diffuse out through the thing.

但首先，这里有一个叫做柔性钩的东西。

But first here, you have this thing called the flexible hook.

它是做什么的？

What does that do?

嗯，它允许旋转，让垂直于膜的这部分能够弯曲，就像一个万向节。

Well, that allows rotation, this perpendicular of the membrane to bend around, acts like a universal joint.

对吧？

Right?

所以它让这里的旋转变成那里的旋转。

So it allows rotation here to turn into rotation there.

而且它的长度是固定的。

And that's of a fixed length.

所有这些，所有这些都在细胞内部，穿过细胞膜，再穿过外膜，在大肠杆菌中。

All of this, all of this down in here inside the cell, all this that goes through the cell membrane out through the outer membrane in E.

所有这些，包括外面这个黄色的部分，就是鞭毛，你看到它有多长，对吧，相对于细胞来说。

Coli, all of that, including And this yellow part out here is the flagella, which is what you see here, how long that is, right, relative to the cell.

这个钩子只是短短的一小段，但它的长度是固定的。

This hook is just a little short thing, but it is of a fixed length.

在某个时刻，底部的机制会知道。

And at some point, the machinery at the base here knows.

它会从输出构成钩子的蛋白质，切换到输出构成鞭毛的蛋白质。

It switches from exporting the proteins that make up this hook to exporting the proteins that make up the flagella.

实际上，有一种叫做“尺子蛋白”的蛋白质，它负责测量长度，当达到那个长度时，它基本上会拉动下面的某个东西，从而改变输出装置输出的特异性。

And actually, there's a protein called the ruler protein that that measures that length, and when it gets to that length, essentially tugs on something down here that changes the specificity of what this export apparatus will will export.

但是你说输出的时候，实际上发生了什么？它不是从基部生长的，而是……不。

But so when you say export, what's really happening, it's not growing from the base, it's actually No.

不。

No.

在顶端生长。

Grows at the tip.

所有东西都在顶端生长。

Everything everything grows at the tip.

它把这些蛋白质输出出去，它们有点像扩散那样移动。

It's exporting these proteins that they kinda diffuse their way

它们穿过中心扩散。

into They the diffuse through the center.

它们可以。

They they can.

中心是空心的。

The center is hollow.

哦，中心是空心的。

Oh, the center is hollow.

好的。

Okay.

这些家伙在远端尖端组装。

And these guys assemble at the at the distal tip.

好的。

Okay.

好的。

Okay.

对吧？

Right?

而且每种情况都有一个帽蛋白，无论是对于罩子还是对于船队，它们防止这些蛋白直接扩散到培养基中。

And there's a cap protein in each case for the hood and for the flotilla that keeps them from just going out into the medium.

对吧？

Right?

它把它们捕获在那里，所以它们在那里组装。

It captures them there, so they get assembled there.

但你是说这在八十年代就已经知道了？

But you're saying this was known in the eighties?

哦，这个在那之前就已经知道了。

Oh, this was known before that.

但他们怎么可能知道所有这些结构呢？

But how how could they have known all these structure?

比如，他们是怎么想出所有这些机制性的东西的？

Like, did they come up with with all this, like, mechanistic?

那是通过遗传学的方法。

It would be genetically.

对吧？

Right?

你知道，通过敲除不同的蛋白质。

You know, by killing different proteins.

你只需要敲除不同的基因。

You just knock you just knock out different genes.

而且，你知道，每个基因，当你把它敲除后，结构会生成到需要那个蛋白质的位置，然后你就能看到那个中间结构。

And, you know, each gene, when you knock it out, the structure will get made to the point where that protein is needed, and you'll see that intermediate structure.

所以你可以逐个敲除基因，看看这些部分是怎么组装的。

So you can go through them, knock out the genes one by one, and see how the pieces

那他们是用电子显微镜观察这些结构的吗，还是？

And is this with, like, electron microscopy they were looking at the structures, or

不是。

No.

不是。

No.

对，就是很简单的。

Yeah, just simple.

很简单。

Simple.

对。

Yeah.

对。

Yeah.

电解。

Electrolysis.

为了让大家感受一下这个问题的复杂性，比如细菌的基因编码，它有多长，需要做多少种排列组合？

Just to give, like, maybe a taste of the complexity of the problem, like, for the gene code of the of the bacteria, like, how long is it and, like, how many permutations you need to do there?

那个

That

嗯，大肠杆菌。

Well, E.

大肠杆菌大约有4万个，抱歉，4千个基因。

Coli has about 40,000 I'm sorry, 4,000 genes.

它有一个环状的染色体，大肠杆菌的。

It has a the the circular chromosome of E.

大肠杆菌的染色体大约有400万，450万个碱基对，编码大约4千个基因。

Coli is about 4,000,000, four and a half million base pairs, and, that encodes about 40 4,000 genes.

所以大约每10万个，抱歉，每千个碱基对应一个基因。

So roughly one gene per 100,000 sorry, per per thousand bases.

顺便说一句，这比人类密集多了，人类只有大约1%的基因编码蛋白质。

By the way, that's way denser than, in humans, like 1% of your gene open codes proteins.

在大肠杆菌里，

In E.

大概有80%到90%的基因都在编码蛋白质，对吧？

Coli, it's like 90 or 80% of the gene open codes proteins, right?

我们的基因之间有很大的间隔空间。

We have big spaces between our genes.

我们的基因里还有内含子，在蛋白质合成之前得把它们切掉。

We also have introns in our genes that have to be cut out before the proteins get made.

总之，他们是通过繁琐的遗传学手段，一个个敲除这些基因，然后观察最终形成的结构。

Anyway, they did that just laboriously genetically, knocking out these genes one by one and seeing what structure got made.

那真是费了不少功夫。

That was a lot of work.

敲除基因，从化学层面来说是怎么回事？

Knocking genes, what is it, like, chemically?

具体是怎么做的？

What do do?

就是产生一些突变。

You got some Mutation.

制造一个突变。

You make a mutation.

现在可以定向做，但当时他们不是定向的。

You can Now now you can do it directed, but they Back then, they weren't doing it directed.

他们只是随机诱变，得到不能游动的东西，然后观察，再把基因定位到染色体上。

They were just randomly mutagenizing and get something that didn't swim, and then look at it, and then map the gene onto the chromosome, right?

他们就这样研究出有多少基因，它们在染色体上怎么排列，哪些基因挨着哪些。

And the way they worked out how many genes there were, how they were organized in the chromosome, which ones genes were next to which ones.

天哪，听起来工作量真大。

Man, sounds like a lot of work.

工作量极其巨大。

It's an enormous amount of work.

日本有个叫伊野的人，是这方面的领头人，所有这些成果都是他建立的。

A guy named Ino, in Japan was the leader in doing this and established all this.

那真是了不起，非常了不起的工作。

It was amazing, amazing work.

所以你看，这里汇聚了很多不同的东西。

So you've got a lot convergence of a lot of different things here coming.

对吧？

Right?

对。

Mhmm.

不同的人在做不同的事情。

Different people doing different things.

是的。

Yeah.

没有这些信息，就很难做到。

Without this information, it would have been hard to Right.

本来可能会继续下去的。

Could have going on.

对。

Right.

你可能会这么想。

You could have thought it.

但事实证明，就那篇论文，其实我，我刚审了一篇论文，讲的是这个开关是怎么工作的，就是当这个钩子达到合适的长度时，在输出装置里有一个蛋白质会改变构象，它从一个非数值环的构象，变成另一种构象，让丝状体能够出来。

But it turns out, just the paper I Actually, I I just reviewed the paper that says how this switch works, that when this gets the right length, there is one protein down here in the export apparatus that changes conformation, And it goes from having it's it's a non numeric ring, goes from one confirmation of that ring that allows things for the hook to get out to another confirmation that allows things for the filament to get out.

而这个变化是由那个尺子蛋白质触发的，当它达到合适的长度时，就会触发输出装置的变化，从而改变它的输出特异性。

And that is triggered by this ruler protein that when it gets to the right length, it triggers the change in the export apparatus that switches its export specificity.

那篇论文，我觉得，我还没被接受，但希望会被接受吧。

That that paper, I think I don't think it's been accepted yet, but hopefully it will be.

太不可思议了。

Incredible.

只是好奇，这个机制有没有被用在别的地方，比如车辆或者其他马达上？

Just out of curiosity, was this mechanism adopted, I don't know, somewhere in vehicles or other motors?

嗯，不是的，因为记住，这里的关键是你不需要任何润滑。

Well, no, because remember, the thing here is that you don't need any lubrication.

对吧？

Right?

在分子层面，所有这些旋转的东西，你不用担心它们会互相摩擦或者什么的。

That's At the molecular level, all this this rotating stuff, you don't have to worry about things grinding against each other or anything like that.

所以，你知道，要把这个应用到任何对人类有用的尺度的马达上，会有很多问题需要解决。

So, you know, to adapt this to any kind of motor on the scale that would be useful for for human things, it'd be a lot of problems that have to be solved.

对吧？

Right?

因为在分子层面你可以做的事情，和宏观层面是完全不同的。

Because you could do things at the molecular level that are very different than what you could do at the macro level.

所以我想在八十年代甚至更早，你有了不同的组件，但没人知道它们是什么形状，我猜。

So I guess in the in the eighties or even earlier, you had the different components, but nobody knew what shape they were, I guess.

当时不知道，比如，所有这些蛋白质的形状是什么样的。

It wasn't known, like, what what was the shape of all these proteins.

哦，你是说各个蛋白质的单独结构？对。

Oh, you mean the individual structure of Yeah.

对，那是随着时间慢慢弄清楚的，主要靠X射线晶体学，对吧？

The yeah, that came out with time as That was basically mainly X-ray crystallography, right?

你得先把这些蛋白质结晶，然后确定它们的结构，也就是X射线结构。

You'd have to crystallize these proteins and determine their structure, their X-ray structure.

现在可以用高分辨率的电子显微镜来获取蛋白质结构。

Now you can do really high resolution EM to get structures of proteins.

但以前你必须能把蛋白质结晶。

But it used to be you had to be able to crystallize protein.

不是所有蛋白质都能结晶，所以那也是个非常费时费力的过程。

Not every protein crystallizes, so that was a very tedious, long process as well.

但所有这些结构最终都弄清楚了，通过制造突变，观察结构在哪个阶段停止发育，从而推断出完整结构。

But all of this got worked out, the structure of all of this got worked out by making mutations and looking at what structures, where the structure stopped developing.

幸运的是，这个过程是按顺序进行的，对吧？

Fortunately, the thing goes at a sequential basis, right?

所以，你知道，如果你有一个突变，这里的底部叫杆，它会旋转，连接到这个，也会旋转，嗯，你有大概五种不同的蛋白质，你敲除其中不同的几种，就会得到不同长度的杆，等等。

So, you know, if you have a mutation, here, the base down here is called the rod, which rotates, which is connected to this, which rotates, well, you you have like five different proteins there, and you knock out different ones of them, and you have a rod of different length, and so forth.

所以这真是令人惊叹，工作量太大了。

So it's just It's amazing, the amount of work.

好。

Okay.

但这里有个关键点。

But here's critical thing.

所以所有这一切，就像我说的，所有这些疑问，所有这些都被制造出来。

So all of this, as I was saying, all of this, all this doubt here, all of this gets made.

但如果你不制造这两种蛋白质，它们叫运动蛋白，负责运动。如果你不制造运动蛋白，马达, 你制造了鞭毛，但它不会旋转。

But if you don't make these two proteins, which are called mote proteins for motility, If you don't make the mote proteins, the motor, you make the flagella, but it doesn't spin.

鞭毛看起来完全正常，但它不会旋转。

Flagella looks perfectly normal, but it doesn't spin.

但如果你拿一个敲除了这些蛋白质的突变体，然后从你克隆了该基因的质粒中表达这些蛋白质，突然马达就开始旋转了。

But if you take a mutant that has knocked out these proteins and you now express those proteins from a plasmid where you've cloned the gene for it, suddenly the motor starts rotating.

我们在这方面做了大量研究，因为事实证明，图中橙色这部分是连接到细胞壁上的，它实际上起到了锚定在细胞壁的作用，而细胞壁是一种非常坚固的结构。

And we did a lot of work on studying because it turns out that that this part that in orange here is connected to the cell wall, so it actually anchors to the cell wall, which is a firm structure.

所以这一部分是固定的，而这部分必须能够运动。

So this is firm, and this part has to move.

下面这部分必须能转动。

The part down here has to move.

对吧？

Right?

我们当时并不清楚这是怎么发生的。

And we didn't know how that happened.

我们知道那个橙色的部分必须附着在细胞壁上。

We knew that the orange guy had to attach to the cell wall.

我们在这方面做了一些研究，发现它必须以正确的方向存在，因为我们观察到一些点突变，也就是只改变单个氨基酸的突变，这会导致失去运动能力；而在其他结构部位出现的补偿性突变又能恢复这种运动能力。

We we did some work on that, and we knew it had to be in the right orientation because we we had mutations, point mutations, ones that just change a single amino acid that would make it non modal, and then we could get compensating mutations in structures here that would restore the motility.

所以你应该明白我的意思了。

So you got the idea.

它必须在正确的空间关系上。

It had to be in the right spatial relationship.

对吧？

Right?

你稍微动一下，它就不工作了。

You move it a little bit, it doesn't work.

然后你动另一个，它又工作了。

Then you move the other one, and it works again.

对吧？

Right?

这个复合物中有没有一些蛋白质，你可以破坏它们，但它们仍然能工作？

Were there proteins that were part of this complex that you could break and they would they would still work?

如果你敲除其中任何一个蛋白质，这个东西在某种程度上就不工作了。

If you knock out any one of those proteins, the thing doesn't work at some level.

我的意思是，有些蛋白质，你敲除它们，就什么都造不出来了。

I mean, some of them some of them, you knock them out, you don't make anything.

对吧？

Right?

那些参与早期组装阶段的蛋白质。

The ones that are involved in the very early stages of assembly.

啊。

Ah.

但是你可以知道这个综合征。

But but you could know the syndrome.

所以如果你删除这部分，它就不起作用了，是的。

So if you delete, like, this part, it's not doing Yeah.

对。

Yeah.

对。

Yeah.

对。

Yeah.

有一件事。

One thing.

如果你移除

If you remove

另一件事，有很多这样的东西。

the other thing There's a whole bunch of them.

这个功能，如果你删除，如果你做一大堆，如果你敲除这个基因，你什么都得不到。

The function if delete if you do whole bunch of them, if you knock out the gene, you don't get anything.

对吧？

Right?

因为有些东西是你开始制造它时必需的。

Because there are certain things you need just to get started in making it.

对吧？

Right?

虽然这信息量不大，因为你只知道，哦，它们甚至不让你开始。

And though that's not very informational because you just know, oh, they they don't let you even get started.

但是其他所有这些步骤，你知道，从制作那个杆，到外面那层外壳，还有周围的LMP环，还有那个衬套，让杆能穿过细胞壁伸出去，等等。

But all these other steps, you know, through making the the the rod and and all the casing around it, LMP rings that are around here, the form of bushing to allow the rod to go out through the out through the cell wall, and yeah.

所有这些。

All of those.

有件事让我特别惊讶，就是你可以有这个旋转轴，但它不会让质子从那个孔漏出来。

Mean, one thing that really surprised me about this is that you can have this spinning axis, but it doesn't leak protons through that hole.

不会。

No.

必须得密封得很紧。

It's gotta be tight.

对吧？

Right?

必须得密封得很紧。

It's gotta be tight.

不能，我是说，必须得极其紧密。

Can't mean, it's gotta be extremely tight.

你不能有洞，绝对不能有洞。

You can't have you cannot have a hole.

那个洞，对。

The hole in Yeah.

膜一旦有洞，质子动力势马上就没了，因为质子会直接从洞里漏过去。

The membrane knocks out the proton motive force right away, because protons just flow through a hole.

我们一会儿会讲到我们在这个马达蛋白上做的一些工作。

And we'll get to that a little bit about the some work we did with this motor protein.

我们知道这个马达蛋白是必需的。

We knew the motor protein was necessary.

我们知道在鞭毛组装完成之后，可以再把马达蛋白加回去。

We knew you could add it back after the flagella was complete.

后来研究发现，这些马达蛋白大多数其实是在膜里自由漂浮的。

And it turns out later work showed that most of these guys are just floating around in the membrane.

所以它是一个嵌入在内膜里的膜蛋白。

So it's a membrane protein embedded in the inner membrane.

当它只是漂浮在膜里的时候，它不会附着到细胞壁上。

It doesn't attach to the cell wall when it's just floating around in the membrane.

当它和马达结合时，这个橙色的部分会竖起来，附着到细胞壁上，然后它就固定住了，因为它是马达的定子，不能移动。

Something about it's engaging with the motor causes this orange part to stick up and attach to the cell wall, and then it stays in place because it's called the stator of the motor because it can't move.

它附着在细胞壁上。

It's attached to the cell wall.

对吧？

Right?

所以你需要这个。

So and you need that.

对吧？

Right?

你必须有一个附着在细胞壁上的东西，才能有东西可以推，让鞭毛转动，而就是这个蛋白质在做这件事。

You have to have something attached to the cell wall in order to have something to push against for the the flagella to turn, and it's this protein that does that.

而且事实证明，即使只有一个也足够了。

And it turns out even one of them is enough.

当鞭毛在自由漂浮时，上面可能只有几个这样的结构。

And when you're turning a free floating flagella, you probably only have a couple of these on the phagella.

但当它要对抗很大的阻力，比如细胞被固定时，上面可能会有多达10到11个这种结构。

When you're turning it against a really high load, like with a tethered cell, then you have up to 10 or 11 of them.

对。

Yeah.

我在准备的时候读到，细胞能感知粘滞度和自身大小来增加定子数量，这点我觉得真的很神奇。

I thought when reading, you know, in preparation for this, I thought it was amazing that the cell can respond to viscosity and its own size Yes.

增加周围的定子数量。

To increase the number of stators around

转动阻力越大，这些单元就越多。

the The greater the resistance of turning it the greater the resistance of turning, the more of these units

这个控制系统具体是怎么运作的？

How get does that control system work?

比如它怎么能感知到阻力大小？这方面研究得清楚吗？

Like, how does it know what the resistance is or like is that well understood?

其实这方面研究得还不透彻。

It's not really well understood.

不过已经做了很多工作。

There's a lot of work done on it.

这项工作最早是我的同事，德州农工大学化学工程系的Pushkar Leila做的，他当时在Howard Berg的实验室做博士后，后来到了德州农工大学继续研究。

It's work that my my colleague, Pushkar Leila, at Texas A and M in the chemical engineering department has worked on initially when he was in Howard Berg's lab as a postdoc, and then after he came to Texas A and M.

大概和扭矩、蛋白质上的扭转有关，这种扭转会让结合细胞壁的那个部分发生变化。我们花了太多时间想观察这个蛋白质是否附着在细胞壁上。

It's something about the torque, the twist on the protein that causes this part that binds the cell wall to be We spent so much time trying to see this protein if it were attached to the cell wall.

我们可以找到其他已知附着在细胞壁上的蛋白质。

We could get other proteins we knew attached to the cell wall.

我们也证明了它们确实附着在细胞壁上。

We could show that they were attached to the cell wall.

我们纯化出了细胞壁。

We would purify the cell walls.

可以纯化出所谓的肽聚糖囊，其实就是细胞壁。

You could purify the, called the murine sac, and it's just a cell wall.

你可以把细胞的其他部分都溶解掉，那个东西还是完整的，附着在上面的蛋白质也就还在。

You could dissolve all the rest of the cell, and that stays intact, and proteins that are stuck to it are attached to it.

但是这个蛋白质，我们一直没找到。

But this protein, we never found it.

后来发现原因是因为它们要等到鞭毛周围的时候才会粘上去。

And it turns out the reason is because they're never attached to that until they're around the flagellar.

在此之前，它们可以随意在膜上飘来飘去。

They could be floating around the membrane as much as you like.

明白吗？

Okay?

还有一件事，我们证明了如果你把这个橙色蛋白质做成一个截短的版本，就是去掉结合细胞壁的那部分，然后在细胞里表达，细胞就停止生长了。

Then one other thing we did was we showed that if you made a truncated version of this protein, this orange protein, okay, that didn't have the part that bound to the cell wall, and you expressed that in the cell, that the cells stopped growing.

然后我们还发现，紧跟着有一段大约10个氨基酸的序列。这个蛋白质的构造是这样的：有两个中心蛋白，就是MotB蛋白的二聚体，然后外面围着五个MotA蛋白，形成一个五聚体。

And then we also showed that there was a little stretch of about 10 amino acids right after so the way the way this protein is made, there are two central proteins, the MotB protein, the dimer, and as we'll see, there's a pentamer of the MotA protein around that.

对吧？

Right?

就在跨膜结构之后。

And there's right after the membrane spanning thing.

所以，MotB蛋白的N端在里面。

So, the N terminus of the MotB protein is inside.

它穿出去。

It goes out.

它刚穿出膜后，有一小段，我们称之为盖子。

Right after it gets out through the membrane, there's a little stretch which we call the lid.

如果你把那10个氨基酸删掉，或者突变其中一个关键的，会发生什么？当你过表达那个蛋白时，细胞突然停止生长。

If you just deleted that, those 10 amino acids, or even mutate one of them that's critical, what happens is that when you express overexpress that protein, suddenly the cells stop growing.

你可以随意过表达正常蛋白。

You could overexpress the normal protein as much as you like.

什么事都没有。

Nothing happens.

过表达缺少盖子或盖子功能异常的蛋白，细胞就会停止生长。

Overexpress the one that lacks that lid or has a malfunctioning lid, and the cells stop growing.

原因是现在质子通道是打开的。

And the reason is because now the proton channel is open.

那个盖子（lid）的作用就是关闭质子通道。

What that lid does is close the proton channel.

明白吗？

Okay?

所以当这些蛋白质只是漂浮在膜上时，通道是关闭的。

So with these things that are just floating around in the membrane, the channel is closed.

只有当它们附着在电机周围时，通道才会打开，盖子会被弹开。

The channel only opens up when you attach around the motor, and that pops off the lid.

所以只有在电机周围时，它才会传导质子。

So the only time it's conducting protons is when you're around the motor.

所以你可以随意制造这种蛋白质，想造多少就造多少。

So you can make as much of this protein as you want, these proteins as you want.

它们漂浮在膜上，什么也不做。

They're floating around the membrane, they don't do anything.

但如果你去掉盖子并过度表达它们，那么现在每个人都在让东西通过，我们证明了实际上你会酸化细胞质，也就是进来的质子，这就是细胞停止生长的原因。

But if you make it without the lid and you overexpress them, now everybody's everybody's letting stuff through, and we showed that you actually acidify the cytoplasm, well, the protons that are coming in, and that's why the cells stop growing.

是只有质子进入细胞，还是也有其他物质？

Is it is it only protons get inside the cell or some other as well?

通过这个通道，只有质子。

Through this, only protons.

现在，当我们说质子通过时，我需要补充一点，可能实际上通过的是水合氢离子。

Now, when we say when we say protons going through, I I should have a caveat here, which is that it maybe was actually going through our hydronium ions.

对。

Right.

H3O。

H h three h three o.

是的。

Yeah.

因为有马达使用钠离子，也有马达使用质子。

Because there are motors that work with sodium and there are motors that work with protons.

结果发现钠离子和水合氢离子的大小差不多。

Turns out the sodium ion is just about the same size as hydronium ion.

所以对我来说，更容易想象的是，其实是水合氢离子过来，结合到那个关键的天冬氨酸残基上。

So actually, it's easier to imagine for me, that it's actually how a hydronium ion that comes there and binds to that critical aspartic acid residue.

如果钠离子能做到，那水合氢离子为什么不行呢？

If a sodium can do it, then why not a hydronium?

而且事实证明，确实有一些罕见的例子，能用钾离子来驱动鞭毛。

And it turns out that there are a few rare ones that can use potassium to drive the flagellum.

所以关键点在于，关键点在于中和那个位于MotB蛋白跨膜区域中间的天冬氨酸残基的电荷。

So the critical thing is, the critical thing is neutralizing the charge of one aspartic acid residue that's in the middle of the membrane spanning region of that central MotB protein.

这种中和是运动所必需的。

That neutralization is required for the motion.

听起来，因为总是有膜，你知道，质子梯度，所以这个好像一直在运转。

And is it it sounds like because there's always a membrane, you know, gradient for for protons, it sounds like this is always on.

就是说，一旦有了这个复合物，它就会一直旋转。

Like, once you have this complex, it's always gonna spin.

哦，是的。

Oh, yeah.

那有没有什么东西在调节它，还是它通常就是一直开着的？

And what is there something that regulates that or it's just generally on?

没有。

No.

没有。

No.

它就是开着的。

It's on.

它一直开着。

It's always on.

所以，这就是……嗯，现在有一些其他研究表明，还有其他方法可以阻止它。

So that that's what Well, there are there's some other work now that shows that there are other things that you can use to stop it.

在一些生物体中，这一点研究得相当透彻。

In some organisms, that's quite well studied.

比如，在枯草芽孢杆菌里，它形成生物膜时会游动，但实际上有一种蛋白质会结合马达，让它停止转动。

Like, for example, in bacillus subtilis, which swims around when it forms a biofilm, there's actually a protein that binds the motor and stops it from turning.

因为事实证明，如果你想形成生物膜，你就不想游来游去。

Because it turns out, if you wanna make a biofilm, you don't wanna be swimming around.

对吧？

Right?

所以，实际上你可以把它关掉。

So there's there's So you can actually shut it off.

还有一些额外的机制可以把它关掉。

Mechanisms that are Additional mechanisms that can shut it off.

对。

Right.

所以，是的，这是一个相当复杂的机器。

So, yeah, this is a pretty sophisticated machine.

我还有一个问题。

Have one more question.

那如果质子通道打开了，为什么细胞会停止生长呢？

So if the the proton channel is opened, why the cell stops growing?

是不是它打乱了那个……

Is it some Is it messes up the

不，它只是让……

No, it just lets

膜电位……

The membrane potential

它让太多质子或氢离子通过，导致细胞质变酸。

It lets so many protons or hydrogen ions through that it acidifies the cytoplasm.

我们只是让细胞来不及把它们泵出去。

We just overwhelm the ability to pump them out fast enough.

所以pH值降低了，而一旦pH值降低，细胞就会停止生长。

So you lower the pH, and whenever you lower the pH, the cells stop growing.

嗯，从基本层面来说，ATP合酶不也是靠同样的质子运行的吗？

Well, just on a basic level, isn't ATP synthase runs on the same protons?

哦，对。

Oh, yeah.

对吧？

Right?

所以基本上，驱动细胞运作的核心机制也是靠质子来工作的。

So basically, the core thing that's like powering the cell also runs on protons.

所以如果你把质子通道短路了，你实际上就是把整个能量系统给短路了，只要你在膜上打个洞

So if you you're short circuiting the you're basically short circuiting the whole energy system if you make a hole in

中间部分。

the middle.

不是的。

No.

你提到了ATP酶。

You mentioned the ATPase.

它会显示出比完全跳跃更晚的旋转。

That it will show that rotated much later than full jump.

他们是怎么搞清楚的，这真的太酷了，ATP酶的结构是怎么弄明白的。

And the way they they did that so this is so cool, how this was figured out, that what was the structure of the ATPase became clear.

后来发现那里有一个质子通道。

Became clear that there was a proton channel.

但ATP酶里的质子通道是个半通道，开口通向一个由10到12个蛋白质组成的环上的天冬氨酸残基。

But the proton channel in the ATPase is a half channel open, leads to the aspartic acid residue in a ring of 10 to 12 proteins.

如果那个天冬氨酸残基带负电，那个环就没法进入膜里。

That ring cannot go into the membrane if that aspartic acid residue is charged negative.

如果质子进来，跟它结合，它就变成中性的了，就能进入膜里了。

If the proton comes in, binds to it, now it's neutral, and it can go into the membrane.

所以过程是这样的：质子从这边进来，所有的天冬氨酸都被质子化了，然后在这边，质子释放到细胞里。

So what happens is it comes in here, all of the guys are protonated, and over here, it comes off into the cell.

所以一个半通道朝外，一个半通道朝内。

So the half channel facing outward and half channel facing inward.

结果发现，鞭毛里的情况也是一样的。

And it turns out that's gonna be the same in the flagellar.

对吧？

Right?

所以质子进来，所有这些都被质子化了，然后旋转，在这里释放出去。

And so it comes in, all these guys are protonated, it turns, and it goes off here.

这意味着你让这个环朝一个方向旋转。

That means you rotate this ring in one direction.

如果你想想制造ATP，对吧，ATP，基本上就是三个反应，酶必须完成这三个反应。

And if you think about making ATP, right, ATP, it's three three reactions, basically, that the enzyme has to do.

它必须结合ADP和无机磷酸盐，必须把它们合成为ATP，然后释放ATP。

It has to bind ADP and inorganic phosphate, It has to combine them to make ATP, and it has to release ATP.

如果你想想这个一、二、三，只有在朝一个方向旋转这个三聚体环时，这个顺序才行得通，反方向就不行。

If you think about that one, two, three, that will only work in that in that order if you rotate in one direction, this trimeric ring, it doesn't work in the other direction.

如果它朝另一个方向转，那你做的就是将ATP分解成ADP和无机磷酸盐，然后释放出去。

If it goes in the other direction, what you do is you split ATP into ADP and inorganic phosphate and release it.

如果你这样做，ATPase就会把质子泵出去。

And if you do that, the ATPase pumps protons out.

是什么决定了它的旋转方向？

What makes the handedness?

是因为ATP合酶的形状吗？是不是像开瓶器那样的螺旋形状？

Is it the shape of the is there like a corkscrew shape in the ATP synthase or like

不是。

No.

不是。

No.

它就是一个三聚体。

It's just it's just a it's a trimer.

但为什么它顺时针转而不是逆时针转呢？

But why does it go clockwise instead of counterclockwise or whatever?

是什么推动的？

Like, what's pushed?

是因为我提到的这个环，对。

Because of this ring that I'm talking about here Mhmm.

如果质子从外面进来，结合在这里，那么环就得往那个方向转，然后在释放之前。

If if protons come in from the outside and bind here, they like, the ring has to go around that way and then before it releases.

如果质子从里面来，结合在这里，那它就往那个方向转，然后释放到外面。

If protons come from the inside, they bind here, then it goes around that way and releases to the outside.

这个环基本上是在往膜里拧进去吧。

The ring is kind of screwing into the membrane, basically.

不是，它就在膜里面。

No, it's just in the membrane.

那为什么朝一个方向旋转就会推动那个……

It's just Why does the rotation in one direction push the

因为有两个半通道。

Because because it there's the two half channels.

对吧？

Right?

如果它朝一个方向转，半通道就向外打开，外部就可以进入。

If it's rotating one way, the half channels open to the outside is accessible.

对吧？

Right?

得转到另一个半通道那里才会释放。

And you don't release until they get around to the other half channel.

反过来，质子从这边进来，其实就是因为质子能量不同。

The other way around, the protons come in here because it's just the difference in the in the energy of the of the protons.

如果内部带负电，质子就会想往这边过来。

If they're if the the inside is negative, the protons are gonna wanna come this way.

如果不是的话，它们就会从另一边过来。

If it's not, they're they're gonna come the other way.

对吧？

Right?

是的。

Mhmm.

对。

Mhmm.

所以我说的这个环，它会朝两个方向旋转。

And so this ring that I'm talking about rotates in two directions.

如果质子进来，它就朝合成ATP的方向转。

If they're coming in, it rotates the way that makes ATP synthesized.

如果它朝另一个方向转，也就是结合ATP、分解ATP，释放ADP和无机磷酸，那它就是在把质子泵出去。

And if it turns the other way, if you're binding ATP, breaking up ATP, and releasing ADP and aerodynamic phosphate, then you're pumping protons out.

结果发现，像链球菌这种没有电子传递链的细胞，它们产生质子动力的方式就是水解ATP，然后通过ATP酶把质子泵出去。

And it turns out that cells, like streptococcus, that don't have an electron transport chain, the way they create their proton motive force is by hydrolyzing ATP and pumping protons out through the ATPase.

明白吗？

Okay?

所以它要么是ATP合酶，要么是ATP酶。

So it's an ATP synthase or an ATPase.

如果它在合成ATP，那就是ATP合酶。

If it's making ATP, it's ATP synthase.

如果它在水解ATP，那就是ATP酶。

If it's hydrolyzing ATP, it's ATPase.

而且这个反应非常倾向于往分解ATP的方向进行。

And the reaction strongly wants to go in the direction of breaking ATP.

这是能量上更有利的方向。

That's the energetically favorable way.

比如，它驱动我们的肌肉，细胞里很多过程都是靠ATP水解来提供能量的，生成ADP和无机磷酸。

It's what powers our muscles, know, for example, all kinds of things in the cell are powered by hydrolysis of ATP, and ADP, inorganic phosphate.

所以你必须要有足够的质子动力来克服形成那个键所需的能量。

So you have to have enough of a proton motive force to overcome that energy that it requires to form that bond.

如果质子动力低于那个水平，ATP就无法正常工作。

If you're below the protomer force goes below that, the ATP just doesn't work.

这时它就会开始水解ATP，并把质子泵出去。

Now it'll start hydrolyzing ATP and pumping pumping protons out.

如果细胞失去了质子动力，它们就会这么做。

And if cells lose their protomer force, that's exactly what they do.

它们会开始水解ATP，并把质子泵出去。

They start hydrolyzing ATP and pumping it out.

比如，如果细胞在无氧条件下生长，大肠杆菌可以无氧生长。

If cells are growing, for example, anaerobically, E.

大肠杆菌可以无氧生长。

Coli can grow anaerobically.

这不是很高效，因为现在它就像链球菌一样。

It's not very efficient because it's it's now it's like the streptococcus.

它只能通过底物水平磷酸化来生成ATP。

It can only use substrate level phosphorylation to make ATP.

但如果它这样做，那么它就必须利用它的ATP酶作为ATP酶来水解ATP并泵出质子，以产生质子动力势，因为质子动力势除了驱动鞭毛外，还需要用于各种其他事情。

But if it's doing that, then it has to use its ATPase as an ATPase to hydrolyze ATP and pump out to make the proton motor force, because the proton motor force is needed for all kinds of things besides driving the flagella.

它对于各种运输系统、很多事情都是必需的。

It's required for all kinds of transport systems, lots of things.

即使你在无氧条件下生长，没有电子传递链，你仍然需要质子动力势。

You need a proton motor force even if you're growing anaerobically where you don't have an electron transport chain.

在那里，ATP酶的作用是产生

And there, the ATPase serves to create the

质子。

the proton.

所以你说这个质子动力势是由外部质子的流动产生的，这一点很有趣。是的。

So it's interesting you're saying that this protomotor force is created by external flow of the Yeah.

是质子而不是细菌利用自身的能量，比如释放ATP然后提供动力

Of the protons instead of the bacteria using its own energy, like ATP releasing it and then powering

是的。

the Yeah.

所以你得这么想，好氧细菌——我是说，你们的线粒体也是这样的。

So you have to the way it aerobic bacteria I mean, your your mitochondria are like this.

对吧？

Right?

你们的线粒体膜上也有ATP酶，跟细菌里的那个基本机制是一样的。

Your mitochondria have an ATPase in the membrane, same basic thing that that the the bacterium has.

在那里，它们一直在合成ATP。

There, they're always making ATP.

对吧？

Right?

因为线粒体膜上总是有质子动力势，质子也总在往里流。

Because you always have the proton motor force across the membrane of the mitochondrion, and you're always having protons moving in.

所以ATP酶总是朝合成ATP的方向转动，你就在不断制造ATP。

And so you're always turning the ATPase in the direction that makes it an ATP synthase, so you're making ATP.

所以在线粒体膜上，有电子传递链把质子泵出去。

So in the membrane of of the mitochondria, you have an electron transport chain that pumps protons out.

在细菌膜上，也有电子传递链把质子泵出去。

In the membrane of the bacteria, you have electron transport chain that pumps protons out.

所以是的。

So yeah.

我的意思是，这其中的能量机制真的非常酷。

I mean, the energetics of that is really, really kinda cool.

确实很了不起。

It is awesome.

确实。

It is

那我们回到刚才的话题，我想我们讲到八十年代了，我们继续吧。

So coming back to I think we were like in the eighties at this point, so let's let's continue.

好的。

Okay.

他们证明ATPase工作原理的方法是，他们把ATPase的膜部分取了出来。

So the a the way that they showed the ATPase worked is that the ATPase, they they took out the the membrane part of the ATPase.

对吧？

Right?

他们只取了旋转的部分，那里有一根杆伸出来，这根杆与膜中转动的环相连，然后他们在那上面粘了一根细丝。

They just took the part that rotates, where there's a rod coming out of it, which is which communicates with the ring that turns in the in the membrane, and they stuck actually a filament onto that.

我忘了那是什么了。

I forget what it was.

好像是肌动蛋白之类的。

It was actin or something.

是抗体。

It was antibodies.

他们把一根细丝粘在那上面，然后加入ATP，就能看到那根细丝开始转动。

They stuck a filament onto that, and when they added ATP, they could see that filament started turning.

所以当这个ATP开始水解时，它带动了这根杆转动。

So when this ATP started hydrolyzing ATP, it turned this rod.

转动的方向就是它泵出质子时的方向。

That would be in the direction it would do when it was pumping protons out.

对吧？

Right?

对。

Mhmm.

这里没有膜，但只要你加入ATP，它就会朝泵出质子的方向转动。

There are no membrane here, so but you just add the ATP and it starts turning in the direction that would pump protons out.

这就证明了ATP酶是旋转的。

So that shows that the ATPase rotated.

那对我们来说真的很激动，因为我们想，哇，也许它们的工作原理是一样的。

And that was, for us, really exciting because we thought, wow, maybe these work the same way.

鞭毛马达和ATP酶，它们的工作原理完全不同。

The flagellar motor and the ATPase, they don't work the same way at all.

但它们都是响应质子穿过膜而旋转，不过机制完全不一样。

But they both rotate in response to the flow of protons through the membrane, but the mechanism is totally different.

还有没有其他类似这种旋转化学的机制？

Any other mechanisms which are similar to this kind of rotation chemistry?

嗯，

Well,

我编辑了一系列《微生物学前沿》的文章。

I I edited a series of articles for frontiers of microbiology.

那叫“生物旋转纳米马达”。

It was called biological rotary nanomotors.

大概有20篇文章，涵盖了所有分子旋转马达。

There are, like, 20 articles, and it it covers all the molecular rotary motors.

我邀请了世界各地的专家来写他们研究领域的章节。

I've got experts from all over the the world to write chapter about what they study.

结果发现，类似鞭毛运动蛋白的结构在很多其他形式中也存在。

And it turns out that the the the structure that's like the the motor proteins of the of the flagellum exists in a lot of other forms.

所以，正如我们稍后可能会谈到的，高分辨率电镜，也就是冷冻电镜，显示那个环状结构由两个中心蛋白和五个围绕在外侧的Mota蛋白组成。

So as as we'll get to, I presume in a moment, this the high resolution EM, cryo EM, showed that their the moat the moat converse consists of two central proteins and then five moat A proteins that are around the outside of that.

对吧？

Right?

这种五加二的结构到处都有。

That five plus two structure exists all over the place.

大概是因为它们都在由质子动力驱动的马达中，所以会旋转，但这些马达连接着各种不同的东西，比如将物质运输到外膜，影响参与细胞壁合成的蛋白质的生成方式，以及为没有鞭毛却在表面滑行的细菌提供动力。

Presumably, it rotates because it's all in motors that are driven by the prothromotive force, but these motors are coupled to the most diverse things, transporting things to the outer membrane, affecting the way proteins are involved in cell wall synthesis are made, powering the gliding bacteria that glide along the surface without flagella at all.

同样的马达，同样的五二马达，在这些不同的环境中都能找到，这是一整套；然后还有另一套，就是ATP酶，那完全不一样。

The same motor, the same five two motor is found in all of these contexts, and that's one whole set, and then there's the other set, which is the ATPs, which is totally different.

它的化学计量比不同，化学机制也不同，完全不一样。

That's has a different stoichiometry, different chemistry, totally different.

但它们共同的特点是能让质子穿过细胞膜。对。

But the thing it has in common is that it lets protons through the membrane Mhmm.

并且在这个过程中引起某种旋转。

And causes something to rotate while it's doing that.

现在，这就涉及到与我们讨论内容直接相关的部分了。

Now, this comes to the part that's really relevant to directly what we're talking about.

不过在做这部分之前，我或许应该先简单讲讲趋化性。

But before before I do that, maybe I should say a little about about the chemotaxis.

所以，在埃希氏菌的两个极上，各有一簇受体。

So there's a cluster of receptors at at water both poles of an E.

大肠杆菌细胞，而且大肠杆菌有五种不同的受体，它们混合在一起形成一个区域。

Coli cell, And their their E.

大肠杆菌有五种不同的受体，它们混杂在一个斑块里。

Coli has five different receptors, and they're in a mixed patch.

这些受体的作用是结合外部的分子，对吧？然后它们会发出跨膜信号，影响细胞质一侧酶的活性。

Now, what these receptors do is they bind molecules on their outer surface, right, and they send a transmembrane signal that affects the activity of an enzyme on the cytoplasmic side.

这个酶的作用是磷酸化一个叫KeyY的小蛋白。

And what that enzyme does is it phosphorylates a small protein called KeyY.

对吧？

Okay?

磷酸化的KeyY会结合到鞭毛马达上，让它顺时针旋转。

And KeyY, in its phosphorylated form, binds to the flagellar motor and causes it to go clockwise.

对吧？

Okay?

所以如果没有信号，没有受体，什么都没有，马达就会一直逆时针转。

So if you have no signal, no receptors, no anything, the motors will always turn counterclockwise.

细胞就会一直直线游动。

The cells will just swim straight forever.

要让它们反向，就需要磷酸化的KeyY，所以还需要所有参与磷酸化的其他成分。

In order to get them to reverse direction, you need this KeY protein in its phosphorylated form, so you also need everything else that's involved in phosphorylating this.

如果缺少这些，就不会有磷酸化的KeyY，马达就总是逆时针转。

If they're missing, then you don't get phosphorylated KeY, and the motor always turns counterclockwise.