FUNCTION OF A MYOSIN HEAVY CHAIN DOMAIN

这项研究将确定肌球蛋白结构域的功能， 一种从头部底部跨越到区域的重链（MHC） 轻链结合的地方。 这个领域可能在 导致动力冲程的构象变化， 肌肉收缩。它还含有已知的突变位点， 家族性肥厚型心肌病（FHC），一种导致突发性心脏病的主要原因， 年轻人的死亡。调查将通过以下方式完成： 在果蝇肌球蛋白缺失基因中表达肌球蛋白重链转基因 变种人 该转基因将编码正常的成人MHC同种型，但将 编码所研究领域的雏形。这将导致 在机械功能的数量变化，因为收缩 成人肌肉纤维的性质与胚胎肌肉有很大的不同。 将测定转基因果蝇的跳跃和飞行能力。的 间接飞行肌和转子背降肌 肌肉（TDT），跳跃肌肉，将通过电子和光检查 显微镜检查超微结构完整性。从动物中分离的肌球蛋白 将测定ATP酶活性和核苷酸结合。的能力 产生力和移动肌动蛋白丝的能力将通过体外 运动性/力产生测定。 最大缩短速度（Vmax） 在分离的IFM和TDT肌肉上测量力的产生 纤维这些试验的结果将揭示这种MHC的影响， 区域对分离的肌球蛋白性质和完整的肌肉功能的影响。 未来 定点突变研究可以确定哪些氨基酸 这对该领域的功能至关重要，并可能提供深入了解为什么 其中一些突变导致FHC和骨骼肌中央核心 疾病

This investigation will determine the function of a domain of the myosin heavy chain (MHC) that spans from the base of the head to the region where the light chains bind. This domain is likely important in the conformational change that causes the power stroke which results in muscle contraction. It also contains known mutation sites that cause familial hypertrophic cardiomyopathy (FHC), a leading cause of sudden death in young adults. The investigation will be accomplished by expressing a myosin heavy chain transgene in a Drosophila myosin-null mutant. The transgene will encode normal adult MHC isoforms, but will encode the embryonic form of the domain under study. This should result in quantitative changes in mechanical function because the contractile properties of adult fibers differ dramatically from embryonic muscles. The transgenic flies will be assayed for jump and flight ability. The indirect flight muscle (IFM) and tergal depressor of the trochanter muscle (TDT), a jump muscle, will be examined by electron and light microscopy for ultrastructure integrity. Myosin isolated from the animals will be assayed for ATPase activity and nucleotide binding. The ability to produce force and move actin filaments will be assessed by in vitro motility/force generation assays. Maximum velocity of shortening (Vmax) and force production will be measured on isolated IFM and TDT muscle fibers. The results of these assays will reveal the influence of this MHC region on isolated myosin properties and intact muscle function. Future site-directed mutant studies can then determine which amino acids are critical for this domain's function, and may provide insight into why some of these mutations lead to FHC and skeletal muscle central core disease.