Harris D E, Warshaw D M
Department of Physiology and Biophysics, University of Vermont, Burlington 05405.
Circ Res. 1993 Jan;72(1):219-24. doi: 10.1161/01.res.72.1.219.
Smooth muscle produces as much stress as skeletal muscle with less myosin. To determine if the actin isoforms specific to smooth muscle contribute to the enhanced force generation, the motility of actin filaments from smooth and skeletal muscle were compared in an in vitro assay in which single fluorescently labeled actin filaments slide over a myosin-coated coverslip. No difference was observed between the velocity of smooth versus skeletal muscle actin filaments over either smooth or skeletal muscle myosin over a large range of assay conditions (changes in pH, ionic strength, and [ATP]). Similarly, no difference was observed between the two actins when the filaments moved under load over mixtures of phosphorylated smooth and skeletal muscle myosin. Thus, it appears that the actin isoforms of smooth and skeletal muscle are mechanically indistinguishable in the motility assay and that smooth muscle's enhanced force generation may originate within the myosin molecule specific to smooth muscle.
平滑肌在肌球蛋白含量较少的情况下能产生与骨骼肌一样大的张力。为了确定平滑肌特有的肌动蛋白同工型是否有助于增强力的产生，在体外实验中比较了平滑肌和骨骼肌肌动蛋白丝的运动性，在该实验中，单个荧光标记的肌动蛋白丝在涂有肌球蛋白的盖玻片上滑动。在大范围的实验条件（pH值、离子强度和[ATP]的变化）下，无论是平滑肌还是骨骼肌的肌动蛋白丝在平滑肌或骨骼肌肌球蛋白上的滑动速度均未观察到差异。同样，当肌动蛋白丝在负载下在磷酸化的平滑肌和骨骼肌肌球蛋白混合物上移动时，也未观察到两种肌动蛋白之间的差异。因此，在运动性实验中，平滑肌和骨骼肌的肌动蛋白同工型在力学上似乎无法区分，平滑肌增强的力产生可能起源于平滑肌特有的肌球蛋白分子内部。
