Reiser P J, Moss R L, Giulian G G, Greaser M L
J Biol Chem. 1985 Aug 5;260(16):9077-80.
Extensive variations exist in the heavy and light chain components of myosin in vertebrate striated muscles. In the present study, we have characterized a specific contractile property, velocity of shortening, and protein subunit composition of single fibers from adult rabbit soleus muscles. Maximum velocity of shortening (Vmax) was measured using the slack test method, and the myosin composition of these same fibers was determined using an ultrasensitive sodium dodecyl sulfate-polyacrylamide gel electrophoresis system. While most fibers were found to have velocities between 0.5 and 1.0 muscle length/s, several had velocities distributed between 1.33 and 2.99 muscle length/s. The fibers in the slower group had myosin subunits that were solely of the slow type; however, those in the faster group contained both fast and slow heavy chains and light chains. The velocity of shortening measured in fibers having both myosin types was highly correlated with the myosin heavy chain composition, with velocity increasing as the proportion of fast-type heavy chain increased. Variations in light chain composition, particularly fast and slow myosin light chain 1, appeared to occur independently of the variations in heavy chain composition, suggesting that some myosin molecules consist of mixtures of slow- and fast-type subunits.
脊椎动物横纹肌中肌球蛋白的重链和轻链成分存在广泛差异。在本研究中，我们对成年兔比目鱼肌单纤维的特定收缩特性、缩短速度和蛋白质亚基组成进行了表征。使用松弛测试法测量最大缩短速度（Vmax），并使用超灵敏十二烷基硫酸钠-聚丙烯酰胺凝胶电泳系统测定这些相同纤维的肌球蛋白组成。虽然发现大多数纤维的速度在0.5至1.0肌肉长度/秒之间，但有几根纤维的速度分布在1.33至2.99肌肉长度/秒之间。较慢组的纤维具有仅为慢型的肌球蛋白亚基；然而，较快组的纤维同时包含快重链和慢重链以及轻链。在具有两种肌球蛋白类型的纤维中测量的缩短速度与肌球蛋白重链组成高度相关，随着快型重链比例的增加，速度也增加。轻链组成的变化，特别是快和慢肌球蛋白轻链1的变化，似乎独立于重链组成的变化发生，这表明一些肌球蛋白分子由慢型和快型亚基的混合物组成。
