Curmi P M, Stone D B, Schneider D K, Mendelson R A
Cardiovascular Research Institute, University of California, San Francisco 94143.
Adv Biophys. 1991;27:131-42. doi: 10.1016/0065-227x(91)90013-4.
Neutron scattering has been used to compare the structure of myosin S1 that is free in solution to that when it is bound to F-actin. To achieve this, deuterated actin was obtained from D. discoideum that had been fed deuterated E. coli. This deuterated actin was rendered "invisible" to neutrons when dissolved in 94% D2O. The neutron scattering patterns obtained from S1 bound to deuterated actin were identical to those of free S1 except for oscillations due to S1's bound to the same actin filament. At low S1 to actin stoichiometries, these oscillations diminish and the patterns become indistinguishable. The apparent radius of gyration of S1 bound to actin is identical to that of free S1 when the stoichiometry is low. Thus, no changes in the structure of S1 were observed to a resolution of 2.5 nm. Computer modelling studies were used to evaluate the compatibility of models for the mechanism of force generation with the neutron data. These studies show that for powerstrokes greater than 5.0 nm, the data are consistent with more than 80% of the crossbridge maintaining a rigid conformation during force generation.
中子散射已被用于比较溶液中游离的肌球蛋白S1与结合到F-肌动蛋白上时的结构。为实现这一点，从喂食了氘代大肠杆菌的盘基网柄菌中获得了氘代肌动蛋白。当溶解在94%的重水中时，这种氘代肌动蛋白对中子变得“不可见”。从结合到氘代肌动蛋白上的S1获得的中子散射图案与游离S1的散射图案相同，只是由于S1结合到同一肌动蛋白丝上而产生的振荡除外。在低S1与肌动蛋白化学计量比时，这些振荡减弱，图案变得难以区分。当化学计量比低时，结合到肌动蛋白上的S1的表观回转半径与游离S1的相同。因此，在2.5纳米的分辨率下未观察到S1结构的变化。计算机建模研究被用于评估力产生机制模型与中子数据的兼容性。这些研究表明，对于大于5.0纳米的动力冲程，数据与超过80%的横桥在力产生过程中保持刚性构象一致。
