Molecular mechanics of mutant cardiac myosin

描述（申请人提供）：家族性肥厚型心肌病（FHC）是一种以心脏肥大、肌原纤维紊乱和猝死为特征的疾病。FHC由肌节蛋白的常染色体显性突变引起。该建议的目的是为肌球蛋白调节轻链（RLC）突变患者的FHC提供分子基础。这些研究是开发减轻心力衰竭影响的治疗方案的必要前提。这些突变定位于可磷酸化丝氨酸，EF手，和MHC的RLC分子的结合区域附近，由于RLC结合区的肌球蛋白被认为是经历大的构象变化，驱动肌肉收缩，我们将解决RLC功能的基本方面和肌球蛋白运动产生的分子基础。我们的方法将利用基于激光陷阱的体外力和运动性测定来评估RLC突变对以下的影响：1）无负荷缩短速度，2）等长力，3）Ca++敏感性和4）突变肌球蛋白集合的功率产生。在单个肌球蛋白分子水平上，将进一步研究整体行为的任何改变，以确定它们是由机械性质的改变还是由肌球蛋白动力学转变速率的变化引起的。我们的方法测量分离的收缩蛋白的机械性质。由于该方法没有使用带皮纤维和全心脏制备物（例如，g.：肌细胞紊乱、纤维化和扩散限制），这是确定FHC突变对肌动球蛋白力和能量产生的直接影响的最纯粹的方法。RLC突变如何影响肌球蛋白的固有功能的知识将允许改变的程度，以更高的功能单位，如心肌纤维，或心脏本身与原发性收缩缺陷。

DESCRIPTION (provided by applicant): Familial hypertrophic cardiomyopathy (FHC) is a disease characterized by cardiac hypertrophy, myofibrillar disarray and sudden death. FHC results from autosomal dominant mutations in sarcomeric proteins. The goal of this proposal is to provide a molecular basis for FHC in patients with mutations in the myosin regulatory light chain (RLC). These studies are a necessary precursor to development of therapeutic protocols that will attenuate the effects of heart failure. The mutations are localized near the phosphorylatable serine, the EF hand, and the MHC binding regions of the RLC molecule and, since the RLC binding region of myosin is thought to undergo large conformational changes that drive muscle contraction, we will address fundamental aspects of RLC function and the molecular basis of myosin motion generation. Our approach will utilize laser-trapbased in vitro force and motility assays to assess the effects of RLC mutations on: 1) unloaded shortening velocity, 2) isometric force, 3) Ca++ sensitivity and 4) power production from mutant myosin ensembles. Any alterations in ensemble behavior will be further pursued at the single myosin molecule level to determine if they result from altered mechanical properties or from changes in the rates ofactomyosin kinetic transitions. Our approach measures the mechanical properties of isolated contractile proteins. Since the method is free from the ambiguities arising from mechanical experiments using skinned fiber and whole heart preparations (e. g.: myocyte disarray, fibrosis, and diffusion limitations), it is the purest way to determine the direct effects of the FHC mutations on actomyosin force and power generation. Knowledge of how the RLC mutations affect myosin's inherent function will allow the degree of alteration to higher functional units, such as the cardiac muscle fiber, or the heart itself to be correlated with a primary contractile defect.