Chemistry and energy transduction in kinesin motor proteins

描述(申请人提供)：真核马达蛋白利用细胞骨架作为道路，在相对较远的距离内运输各种细胞内的货物。ATP与水反应生成ADP和无机磷是马达蛋白启动关键细胞功能的中心和主要步骤，包括有丝分裂过程中的染色体分离、基因复制、转录和囊泡和细胞器的运输。这些纳米电机的功能都是通过消耗这种能量并将化学中间体耦合到一系列推动细胞净运动的构象变化来发挥作用的。对于肌动蛋白来说，这种催化反应及其化学机械转导的缺陷与人类的癌症、发育障碍、肌病和神经退行性疾病有关。虽然预测了在ATP水解和机械转导过程中中间状态的复杂序列，但通过直接结构观察只验证了一小部分状态。因此，目前关于原子水平相互作用的经验证据不足以评估生物ATP水解及其伙伴能量转导中完整的化学步骤范围。我们实验室的最新数据捕捉到了关键的催化中间体，这些中间体解决了有关机理的现有问题，并为进一步的进展提供了新的框架。在这些发现的基础上，我们的主要目标是确定质子转移和氢键在人类Kinesin-5蛋白的ATP水解和化学-机械耦合中的新作用，Kinesin-5蛋白是有丝分裂所必需的，也是癌症治疗的靶点。要测试的问题是，在ATP水解的第一步中，化学参与者的身份，活性位点两侧的环是否在酶的过渡状态中发生构象变化，以及中心2-折叠是否具有将信息从活性位点传递到其他位点的作用。预期答案的意义是双重的。由于化学和运动是同义反复联系的，因此需要这些信息来阐明纳米电机中运动的分子机制，目前这些缺陷尚不清楚。此外，获得的实验证据将使针对人类激动素-5的抗癌药物的合理设计成为可能。

DESCRIPTION (provided by applicant): Eukaryotic motor proteins utilize the cytoskeleton as roadways to transport a variety of intracellular cargo across relatively vast distances. The reaction of ATP with water to produce ADP and inorganic phosphate is the central and primary step in motor proteins that initiates critical cellular functions, including chromosome segregation during mitosis, gene replication, transcription, and transport of vesicles and organelles. These nanomotors all function by consuming this energy and coupling the chemical intermediates to a series of conformational changes that propel net celular motion. For kinesins, defects in this catalytic reaction and its chemo-mechanical transduction are linked to cancer, developmental errors, myopathies, and neurodegenerative conditions in humans. Although a complex sequence of intermediate states during ATP hydrolysis and mechanotransduction is predicted, only a small subset of states has been validated by direct structural observation. Thus, current empirical evidence of atomic-level interactions is not sufficient to assess the complete range of chemical steps in biological ATP hydrolysis and its partnered energy transduction. Recent data from our laboratories has captured key catalytic intermediates that resolve extant questions regarding mechanism and provide a new framework for further progress. Building upon these findings, our principal goal is to define novel roles for proton transfer and hydrogen bonding for ATP hydrolysis and chemo-mechanical coupling in the human Kinesin-5 protein, essential for mitosis and a target for cancer therapeutics. Questions to be tested are the identity of the chemical player in the first step of ATP hydrolysis, whether loops flanking the active site undergo conformational changes in the enzyme transition state, and if the central 2-sheet has a role in transducing information from the active site to other sites. The significance of the anticipated answers is twofold. As chemistry and motion are tautologically linked, this information is required to illuminate molecular mechanisms of motion in nanomotors, which are currently unclear from these deficits. Moreover, garnered experimental evidence will allow rational design of anti-cancer drugs directed against human Kinesin-5.