Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA.
Biophys J. 2011 Sep 7;101(5):1114-22. doi: 10.1016/j.bpj.2011.07.045.
Structural interactions between the myosin converter and relay domains have been proposed to be critical for the myosin power stroke and muscle power generation. We tested this hypothesis by mutating converter residue 759, which interacts with relay residues I508, N509, and D511, to glutamate (R759E) and determined the effect on Drosophila indirect flight muscle mechanical performance. Work loop analysis of mutant R759E indirect flight muscle fibers revealed a 58% and 31% reduction in maximum power generation (P(WL)) and the frequency at which maximum power (f(WL)) is generated, respectively, compared to control fibers at 15 °C. Small amplitude sinusoidal analysis revealed a 30%, 36%, and 32% reduction in mutant elastic modulus, viscous modulus, and mechanical rate constant 2πb, respectively. From these results, we infer that the mutation reduces rates of transitions through work-producing cross-bridge states and/or force generation during strongly bound states. The reductions in muscle power output, stiffness, and kinetics were physiologically relevant, as mutant wing beat frequency and flight index decreased about 10% and 45% compared to control flies at both 15 °C and 25 °C. Thus, interactions between the relay loop and converter domain are critical for lever-arm and catalytic domain coordination, high muscle power generation, and optimal Drosophila flight performance.
肌球蛋白转换器和中继域之间的结构相互作用被认为对肌球蛋白力臂运动和肌肉发力至关重要。我们通过突变与中继残基 I508、N509 和 D511 相互作用的转换器残基 759（R759E）来检验这一假设，并确定其对果蝇间接飞行肌机械性能的影响。突变体 R759E 间接飞行肌纤维的工作循环分析显示，与 15°C 时的对照纤维相比，最大发电功率（P（WL））和最大功率生成频率（f（WL））分别降低了 58%和 31%。小振幅正弦分析显示，突变体弹性模量、粘性模量和机械速率常数 2πb 分别降低了 30%、36%和 32%。从这些结果推断，该突变降低了通过产生工作的横桥状态的转变和/或在强结合状态下产生力的速率。肌肉功率输出、刚度和动力学的降低与生理相关，因为与对照果蝇相比，突变果蝇的翅膀拍打频率和飞行指数在 15°C 和 25°C 时分别降低了约 10%和 45%。因此，中继环和转换器域之间的相互作用对于杠杆臂和催化域的协调、高肌肉发力和优化的果蝇飞行性能至关重要。
