VanBuren P, Harris D E, Alpert N R, Warshaw D M
Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, USA.
Circ Res. 1995 Aug;77(2):439-44. doi: 10.1161/01.res.77.2.439.
The two mammalian cardiac myosin heavy chain isoforms, alpha and beta, have 93% amino acid homology, but hearts expressing these myosins exhibit marked differences in their mechanical activities. To further understand the function of these cardiac myosins as molecular motors, we compared the ability of these myosins to hydrolyze ATP and to both translocate actin filaments and generate force in an in vitro motility assay. V1 myosin has twice the actin-activated ATPase activity and three times the actin filament sliding velocity when compared with V3 myosin. In contrast, the force-generating ability of these myosins is quite different when the total force produced by a small population of myosin molecules (> 50) is examined. V1 myosin produces only one half the average cross-bridge force of V3 myosin. With discrete areas of primary structural heterogeneity known to exist between alpha and beta heavy chains, the differences we report in the hydrolytic and mechanical activities of the motors are explored in the context of potential structural and kinetic differences between the V1 and V3 myosins.
两种哺乳动物心肌肌球蛋白重链亚型，α和β，具有93%的氨基酸同源性，但表达这些肌球蛋白的心脏在机械活性方面表现出显著差异。为了进一步了解这些心肌肌球蛋白作为分子马达的功能，我们在体外运动分析中比较了这些肌球蛋白水解ATP、使肌动蛋白丝移位以及产生力的能力。与V3肌球蛋白相比，V1肌球蛋白的肌动蛋白激活ATP酶活性是其两倍，肌动蛋白丝滑动速度是其三倍。相比之下，当检查少量肌球蛋白分子（>50个）产生的总力时，这些肌球蛋白产生力的能力有很大不同。V1肌球蛋白产生的平均横桥力仅为V3肌球蛋白的一半。已知α和β重链之间存在主要结构异质性的离散区域，我们在V1和V3肌球蛋白潜在的结构和动力学差异的背景下，探讨了我们所报道的马达水解和机械活性的差异。
