Xie Ping
Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
J Theor Biol. 2020 Apr 7;490:110173. doi: 10.1016/j.jtbi.2020.110173. Epub 2020 Jan 23.
Biomolecular motors make use of free energy released from chemical reaction (typically ATP hydrolysis) to perform mechanical motion or work. An important issue is whether a molecular motor exhibits tight or non-tight chemomechanical (CM) coupling. The tight CM coupling refers to that each ATPase activity is coupled with a mechanical step, while the non-tight CM coupling refers to that an ATPase activity is not necessarily coupled with a mechanical step. Here, we take kinesin, monomeric DNA helicase, ring-shaped hexameric DNA helicase and ribosome as examples to study this issue. Our studies indicate that some motors such as kinesin, monomeric helicase and ribosome exhibit non-tight CM coupling under hindering forces, while others such as the ring-shaped hexameric helicase exhibit tight or nearly tight CM coupling under any force. For the former, the reduction of the velocity caused by the hindering force arises mainly from the reduction of the CM coupling efficiency, while the ATPase rate is independent or nearly independent of the force. For the latter, the reduction of the velocity caused by the hindering force arises mainly from the reduction of the ATPase rate, while the CM coupling efficiency is independent or nearly independent of the force.
生物分子马达利用化学反应（通常是ATP水解）释放的自由能来执行机械运动或功。一个重要的问题是分子马达是否表现出紧密或非紧密的化学机械（CM）偶联。紧密的CM偶联是指每个ATP酶活性与一个机械步骤偶联，而非紧密的CM偶联是指一个ATP酶活性不一定与一个机械步骤偶联。在这里，我们以驱动蛋白、单体DNA解旋酶、环状六聚体DNA解旋酶和核糖体为例来研究这个问题。我们的研究表明，一些马达，如驱动蛋白、单体解旋酶和核糖体，在阻碍力下表现出非紧密的CM偶联，而其他一些，如环状六聚体解旋酶，在任何力下都表现出紧密或近乎紧密的CM偶联。对于前者，阻碍力导致的速度降低主要源于CM偶联效率的降低，而ATP酶速率与力无关或几乎与力无关。对于后者，阻碍力导致的速度降低主要源于ATP酶速率的降低，而CM偶联效率与力无关或几乎与力无关。
