Billeter R, Heizmann C W, Howald H, Jenny E
Eur J Biochem. 1981 May 15;116(2):389-95. doi: 10.1111/j.1432-1033.1981.tb05347.x.
In this study, myosin types in human skeletal muscle fibers were investigated with electrophoretic techniques. Single fibers were dissected out of lyophilized surgical biopsies and typed by staining for myofibrillar ATPase after preincubation in acid or alkaline buffers. After 14C-labelling of the fiber proteins in vitro by reductive methylation, the myosin light chain pattern was analysed on two-dimensional gels and the myosin heavy chains were investigated by one-dimensional peptide mapping. Surprisingly, human type I fibers, which contained only the slow heavy chain, were found to contain variable amounts of fast myosin light chains in addition to the two slow light chains LC1s and LC2s. The majority of the type I fibers in normal human muscle showed the pattern LC1s, LC2s and LC1f. Further evidence for the existence in human muscle of a hybrid myosin composed of a slow heavy chain with fast and slow light chains comes from the analysis of purified human myosin in the native state by pyrophosphate gel electrophoresis. With this method, a single band corresponding to slow myosin was obtained; this slow myosin had the light chain composition LC1s, LC2s and LC1f. Type IIA and IIB fibers, on the other hand, revealed identical light chain patterns consisting of only the fast light chains LC1f, LC2f and LC3f but were found to have different myosin havy chains. On the basis of the results presented, we suggest that the histochemical ATPase normally used for fibre typing is determined by the myosin heavy chain type (and not by the light chains). Thus, in normal human muscle a number of 'hybrid' myosins were found to occur, namely two extreme forms of fast myosins which have the same light chains but different heavy chains (IIA and IIB) and a continuum of slow forms consisting of the same heavy chain and slow light chains with a variable fast light chain composition. This is consistent with the different physiological roles these fibers are thought to have in muscle contraction.
在本研究中，运用电泳技术对人类骨骼肌纤维中的肌球蛋白类型进行了研究。从冻干的手术活检组织中分离出单根纤维，并在酸性或碱性缓冲液中预孵育后，通过肌原纤维ATP酶染色对其进行分型。在体外通过还原甲基化对纤维蛋白进行14C标记后，在二维凝胶上分析肌球蛋白轻链模式，并通过一维肽图分析研究肌球蛋白重链。令人惊讶的是，仅含慢速重链的人类I型纤维，除了两条慢速轻链LC1s和LC2s外，还含有数量不等的快速肌球蛋白轻链。正常人类肌肉中的大多数I型纤维呈现出LC-1s、LC-2s和LC-1f的模式。通过焦磷酸凝胶电泳对天然状态下的纯化人类肌球蛋白进行分析，进一步证明了人类肌肉中存在由慢速重链与快速和慢速轻链组成的杂合肌球蛋白。用这种方法，得到了一条对应于慢速肌球蛋白单一谱带；这种慢速肌球蛋白的轻链组成为LC1s、LC2s和LC1f。另一方面，IIA型和IIB型纤维显示出相同的轻链模式，仅由快速轻链LC1f、LC2f和LC3f组成，但发现它们具有不同的肌球蛋白重链。根据所呈现的结果，我们认为通常用于纤维分型的组织化学ATP酶是由肌球蛋白重链类型决定的（而非轻链）。因此，在正常人类肌肉中发现存在多种“杂合”肌球蛋白，即两种极端形式的快速肌球蛋白，它们具有相同的轻链但重链不同（IIA型和IIB型），以及一系列由相同重链和慢速轻链组成且快速轻链组成可变的慢速形式。这与这些纤维在肌肉收缩中被认为具有的不同生理作用是一致的。
