The single polypeptide type I restriction enzymes - minimal multifunctional molecular motors

为了让生活变得更简单，人类开发了承担复杂任务的机器。但大自然首先到达了那里；地球上的生命依赖于微型机器和马达的活动，这些机器和马达不是由金属齿轮和齿轮制成的，而是由蛋白质制成的。微型工厂现在正在你的身体里工作！以你的遗传物质DNA为例。有很多“分子马达酶”，它们的任务是识别DNA的特定部分(由称为A、G、C和T的化学碱基组成的序列)，然后将化学能(以一种名为ATP的燃料化合物的形式)转化为机械事件。例如，我们研究的蛋白质一次沿着DNA移动数千个碱基，就像火车沿着轨道移动一样。一旦这些马达到达DNA中的一个定义点，它们就会停下来，并使用额外的酶活性来切断轨迹。虽然这似乎是发动机的破坏性事件，但它对细胞的健康至关重要，因为这些切割不是在宿主基因组中进行的，而是针对入侵的病毒DNA。我们希望研究的酶的一个显著特征是，所有这些复杂性都包含在单一蛋白质中，有点像手机，它同时也是相机、游戏机和MP3播放器。如何将所有多种酶的活性包含在一个蛋白质单位中，以及如何协调这些活性，以便马达能够以受控的方式沿着DNA移动？这就是我们想要找出的。

To make life more straightforward, Mankind has developed machines to undertake complex tasks. But Nature got there first; life on Earth is reliant on the action of microscopic machines and motors made not from metal gears and cogs but from proteins. Miniaturised factories are working in your body right now! Take for example your genetic material, DNA. There are a great many 'molecular motor enzymes' whose task is to recognise a specific part of the DNA (a sequence made up of chemical bases called A, G, C and T) and then to convert chemical energy (in the form of a fuel compound called ATP) into mechanical events. For example, the proteins we study move along DNA many thousands of bases at a time, much like a train along a track. Once these motors reach a defined point in the DNA they stop and cut the track using an additional enzyme activity. Whilst this may seem a destructive event for the motor, it is vital to the health of the cell because these cuts are not made in the host genome but are targeted to invading viral DNA. A remarkable feature of the enzymes we wish to study is that all this complexity is contained within a single protein, a bit like a mobile phone which is also a camera, a games console and an MP3 player. How can all the multiple enzyme activities be contained in one protein unit and how are the activities coordinated so that the motor can move along DNA in a controlled fashion? This is what we intend to find out.