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Molecular Energetics of Protein Motors

蛋白质马达的分子能量学

基本信息

批准号：
06304052
负责人：
KODAMA Takao
金额：
$ 10.5万
依托单位：
KYUSHU INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06304052/
关键词：
chemomechanical coupling hydrophobic hydrophilc transition single molecule physiology thermal fluctuation ATP ase vectorial motion intramolecular hydrogen-bond motor molecule エナジェティックス X線小角散乱誘電分散急速凍結法 in vitro 運動系張力ゆらぎ 1分子

项目摘要

Energetic aspects of protein motors were investigated by various methods including microwave-dielectric spectroscopy and calorimetry of myosin motors hydrolyzind ATP,direct observation of simgle kinesin molecules moving along microtubules, imaging of individual ATP turnovers by single myosin molecules, small-angle X-ray diffeaction of myosin molecules with diffrrent bound nucleotides, X-ray diffraction of muscle, X-ray crystallography of myosin complexed with different nucleotides, diffusion-enhanced fluorescence resonance energy transfer of actin molecules, simulation of solvation free-energy of protein motors, fluctuation analysis of kinesin sliding along microtubule, stereo-photogramtry of quick-freeze deep-etch replica images of motor proteins, and site-directed mutagenesis of motor proteins. These studies indicate that :1.the myosin surface hydrophobicity change plays a crucial role in the enthalpy-entropy compensation effectc observed in the steps of myosin ATP hydrolysis ;2.protein motors can modulate the mode of coupling between chemical change (ATP hydrolysis) and mechanical output depending on load imposed on them. Thus, the energy of ATP hydrolys is somehow stored in the motor protein, which is used fractionally at each power stroke cycle. This would mean that the protein motor operate with energy conversion efficiency as high as more than 50% using the energy input comparable to or marginally above the thermal energy ;3.Of two negative potential sites of actin molecule surface, one around the myosin binding site while the other site around the phalloidin binding site is not significantly affected ;4.an effective diffusion coefficient from displacement fluctuations of a sliding filament obtained from its single noisy trajectory is a useful parameters for constructing the models for mechanochemical coupling.

通过多种方法研究了蛋白质马达的能量方面，包括微波介电光谱和肌球蛋白马达水解ATP的量热法，单个肌球蛋白分子沿微管运动的直接观察，单个肌球蛋白分子的ATP转换成像，不同结合核苷酸的肌球蛋白分子的小角度x射线衍射，肌肉的x射线衍射，肌球蛋白与不同核苷酸络合的x射线晶体学，肌动蛋白分子的扩散增强荧光共振能量转移，蛋白质马达的溶剂化自由能模拟，马达蛋白沿微管滑动的波动分析，马达蛋白速冻深蚀刻复制图像的立体摄影测量，以及马达蛋白的定点诱变。这些研究表明：1。1 .肌球蛋白表面疏水性的变化在肌球蛋白ATP水解过程中观察到的焓-熵补偿效应中起着至关重要的作用；蛋白质马达可以调节化学变化（ATP水解）和机械输出之间的耦合模式，这取决于施加在它们身上的负荷。因此，ATP水解的能量以某种方式储存在马达蛋白中，在每个动力冲程循环中使用少量能量。这意味着蛋白质马达使用与热能相当或略高于热能的能量输入，其能量转换效率可高达50%以上；3 .在肌动蛋白分子表面的两个负电位位点中，一个位于肌凝蛋白结合位点附近，另一个位于阳鞘苷结合位点附近，不受明显影响；从单噪声轨迹中得到的滑动丝位移波动的有效扩散系数是建立机械-化学耦合模型的一个有用参数。