Post translational modifications tune cardiac myosin

摘要 我们假设人类重链的翻译后修饰(PTM) 心肌肌球蛋白头部(S1)调节肌球蛋白变构在两个不同状态之间的转换， 活跃，准备与肌动蛋白相互作用时，肌球蛋白S1处于隔离的超松弛状态 结合到肌球蛋白尾部的近端S2结构域，并受相互作用的空间制约 加入肌动蛋白。肌球蛋白结构状态之间的快速和可逆转换可能是一种调节 当更活跃的头部在肌节中变得可用时肌肉激活的机制 部队生产。这项建议是基于(A)我们最近在表达上的成功和 使用C2C12小鼠成肌细胞表达系统纯化人心肌肌球蛋白，以及 (B)成功应用一套补充生物物理方法进行研究 肌球蛋白和肌动球蛋白动力学、肌球蛋白运动和肌球蛋白S1-S2相互作用。我们建议 研究三个人心肌肌球蛋白的PTM模拟突变体。我们将研究 突变对肌动球蛋白循环动力学、肌球蛋白S1和肌球蛋白亲和力的影响 近端S2，肌球蛋白种群处于隔离的SRX状态，并卸载和加载 PTM模拟肌球蛋白构建物的体外运动性。这项提议的两个目的是 互补性。肌动球蛋白循环的变化动力学将在瞬变过程中被检测到 肌动蛋白微丝在体外卸载过程中的动力学实验及变化速度 运动性分析。受影响的SRX状态的稳定性将直接在单个 周转率测定，将被检测为改变的肌球蛋白床的总力 负荷式体外运动试验。因此，我们将检验我们的假设，即PTM 破坏肌球蛋白SRX状态的稳定性，并将表征PTM对人类心脏的影响 肌球蛋白的动力学和运动性。

ABSTRACT We hypothesize that the post-translational modification (PTM) of the heavy chain of human cardiac myosin head (S1) regulates myosin allosteric transition between two distinct states, active, ready to interact with actin and the sequestered super-relaxed state when myosin S1 bound to the proximal S2 domain of myosin tail and sterically constrained from the interaction with actin. Rapid and reversible switch between myosin structural states could be a regulatory mechanism of muscle activation when more active heads become available in a sarcomere for force production. The proposal is based on (a) our recent success in the expression and purification of human cardiac myosin using the C2C12 murine myoblasts expression system, and (b) on the successful application of a toolset of complementary biophysical methods to study myosin and actomyosin kinetics, myosin motility, and myosin S1-S2 interactions. We propose to study three selected PTM-mimetic mutants of the human cardiac myosin. We will examine the effect of mutations on the kinetics of the actomyosin cycle, the binding affinity of myosin S1 and proximal S2, the population of myosin in the sequestered SRX state, and unloaded and loaded in vitro motility of the PTM-mimetic myosin constructs. Two aims of the proposal are complementary. The changed kinetics of the actomyosin cycle will be detected in the transient kinetics experiments and as the changed velocity of actin filament in the unloaded in vitro motility assay. The affected stability of the SRX state will be assessed directly in the single turnover ATP assay and will be detected as changed ensemble force of myosin bed in the loaded in vitro motility assay. As the result, we will examine our hypothesis that PTM destabilizes the SRX state of myosin and will characterize the effect of PTM on human cardiac myosin kinetics and motility.