Sugiura S, Yamashita H, Sata M, Momomura S, Serizawa T, Oiwa K, Chaen S, Shimmen T, Sugi H
Second Department of Internal Medicine, School of Medicine, University of Tokyo, Japan.
Biochim Biophys Acta. 1995 Aug 15;1231(1):69-75. doi: 10.1016/0005-2728(95)00062-n.
The difference in kinetic properties between two myosin isozymes (V1 and V3) in rat ventricular myocardium was studied by determining the steady-state force-velocity (P-V) relations in the ATP-dependent movement of V1 and V3-coated polystyrene beads on actin cables of giant algal cells mounted on a centrifuge microscope. The maximum unloaded velocity of bead movement was larger for V1 than for V3. The velocity of bead movement decreased with increasing external load applied by the centrifuge microscope, and eventually reached zero when the load was equal to the maximum isometric force (P0) generated by the myosin heads. The maximum isometric force P0 was less than 10 pN, and did not differ significantly between V1 and V3. The P-V curves consisted of a hyperbolic part in the low force range and a non-hyperbolic part in the high force range. The critical force above which the curve deviated from the hyperbola was much smaller for V1 than for V3. An analysis using a model with an extremely small number of myosin heads involved in the bead movement suggested a marked difference in kinetic properties between V1 and V3.
通过在安装于离心显微镜上的大型藻类细胞的肌动蛋白纤维上，测定包被有V1和V3的聚苯乙烯珠在ATP依赖运动中的稳态力-速度（P-V）关系，研究了大鼠心室心肌中两种肌球蛋白同工酶（V1和V3）的动力学特性差异。V1包被珠的最大空载运动速度大于V3包被珠。珠的运动速度随着离心显微镜施加的外部负荷增加而降低，当负荷等于肌球蛋白头部产生的最大等长力（P0）时，速度最终降至零。最大等长力P0小于10 pN，V1和V3之间无显著差异。P-V曲线在低力范围内由双曲线部分组成，在高力范围内由非双曲线部分组成。V1曲线偏离双曲线的临界力远小于V3。使用一个涉及参与珠运动的肌球蛋白头部数量极少的模型进行分析，表明V1和V3在动力学特性上存在显著差异。
