Berman M R, Lord C C, Maughan D W
Department of Physiology and Biophysics, University of Vermont, Burlington 05405.
J Mol Cell Cardiol. 1988 Aug;20(8):679-87. doi: 10.1016/s0022-2828(88)80013-0.
Values of mechanical and biochemical indicators of muscle performance measured in heart muscle having mostly the V1 isoenzyme of myosin are different than measurements of the same indicators made in muscle having mostly the V3 isoenzyme of myosin. It has been suggested that these differences in performance indicators might be attributable to subtle differences in myosin-actin crossbridge cycling kinetics between the V1 and the V3 isoforms of myosin. To investigate this, we derived information about myosin-actin cycling kinetics from the time course of force transients following rapid small amplitude length releases applied to chemically "skinned", isometrically contracting trabeculae from the hearts of normal (greater than = 90% V1) and propylthiouracil treated (greater than = 90% V3) rats. The rate constant for rapid force recovery measured in trabeculae from normal rats was twice that measured in trabeculae from treated rats (88.8 +/- 18.8 (n = 12) vs. 43.7 +/- 6.5 (n = 10)/s, mean +/- S.D.). We interpret this difference in rate constants as evidence that the kinetics of at least one step in the interaction of myosin with actin depends on the isoenzyme of myosin present in the heart.
在主要含有肌球蛋白V1同工酶的心肌中测得的肌肉性能的力学和生化指标值，与在主要含有肌球蛋白V3同工酶的肌肉中测得的相同指标不同。有人提出，这些性能指标的差异可能归因于肌球蛋白V1和V3同工型之间肌球蛋白-肌动蛋白横桥循环动力学的细微差异。为了研究这一点，我们从对正常大鼠（≥90% V1）和丙硫氧嘧啶处理大鼠（≥90% V3）心脏的化学“去皮”、等长收缩小梁施加快速小幅度长度释放后力瞬变的时间过程中，获得了有关肌球蛋白-肌动蛋白循环动力学的信息。在正常大鼠小梁中测得的快速力恢复速率常数是在处理大鼠小梁中测得的两倍（88.8±18.8（n = 12）对43.7±6.5（n = 10）/秒，平均值±标准差）。我们将速率常数的这种差异解释为证据，表明肌球蛋白与肌动蛋白相互作用中至少一个步骤的动力学取决于心脏中存在的肌球蛋白同工酶。
