Schoenberg M
Laboratory of Physical Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Biophys J. 1991 Sep;60(3):690-6. doi: 10.1016/S0006-3495(91)82098-7.
The effect of ionic strength on the kinetics of myosin cross-bridges in the presence of the ATP analogue PP, has been examined. It was found that increasing ionic strength from moderate values (mu approximately 100 mM) to high values (mu approximately 200 mM) has three effects. It causes a big decrease in the half time for the force decay after a small stretch, it causes a significant decrease in the sigmoidicity of the nucleotide analogue concentration dependence of the "apparent rate constant" of force decay after a small stretch, and it causes a big decrease in the range of rate constants necessary to describe the multiexponential force decay. It causes the last of these by causing a much larger increase in the slowest rate constants of the decay than in the fastest rate constants. The results suggest that whereas the behavior of cross-bridges in the presence of ATP is well-described by the simple independent-head equilibrium cross-bridge model of Schoenberg (1985. Biophys. J. 48:467-475), cross-bridges in the presence of the ATP analogue PPi require the more complicated double-headed equilibrium cross-bridge model of Anderson and Schoenberg (1987. Biophys. J. 52: 1077-1082) to describe their behavior.
研究了离子强度对存在ATP类似物PPi时肌球蛋白横桥动力学的影响。发现离子强度从中等值（μ约100 mM）增加到高值（μ约200 mM）有三个作用。它会使小拉伸后力衰减的半衰期大幅缩短，会使小拉伸后力衰减的“表观速率常数”对核苷酸类似物浓度依赖性的S形显著降低，还会使描述多指数力衰减所需的速率常数范围大幅减小。它通过使衰减最慢的速率常数比最快的速率常数增加得多来导致最后一个结果。结果表明，虽然在ATP存在下横桥的行为可以用Schoenberg（1985年。《生物物理杂志》48:467 - 475）的简单独立头部平衡横桥模型很好地描述，但在ATP类似物PPi存在下的横桥需要Anderson和Schoenberg（1987年。《生物物理杂志》52:1077 - 1082）更复杂的双头平衡横桥模型来描述其行为。
