Mykles D L
Department of Biology, Colorado State University, Fort Collins 80523.
J Exp Zool. 1988 Mar;245(3):232-43. doi: 10.1002/jez.1402450303.
Myofibrillar proteins in muscles of the claws and abdomen of lobster, Homarus americanus, and the claws of fiddler crab, Uca pugnax, and land crab, Gecarcinus lateralis, have been analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fibers contained numerous isoforms of structural and regulatory proteins in assemblages correlated with fiber type. One fast (F) and two slow (S1 and S2) fibers were identified. All F fibers possessed two isoforms of paramyosin (P1 and P2), while all slow fibers, with the exception of Uca major claw, contained only the P2 variant. S1 and S2 fibers were distinguished by the distribution of a large isoform of troponin-T (T1; Mr = 55,000); S2 fibers in all three species contained T1 in addition to one or two smaller-molecular-weight variants usually associated with S1 fibers. In order to determine whether the slow fibers differed in histochemical properties, land crab claw closer muscle was cryosectioned and stained for myofibrillar ATPase and NADH diaphorase activities. Most S2 fibers had lower ATPase and higher NADH diaphorase activities than S1 fibers, which indicated that S2 fibers had a lower rate of contraction and were more fatigue-resistant than S1 fibers. It is proposed that the S1 and S2 fibers defined by biochemical and histochemical criteria are identical to the slow-twitch and tonic fibers, respectively characterized physiologically.
利用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳对美洲螯龙虾的爪和腹部肌肉、招潮蟹的爪以及地蟹的爪中的肌原纤维蛋白进行了分析。纤维中含有大量与纤维类型相关的结构蛋白和调节蛋白的同工型。鉴定出了一条快肌纤维（F）和两条慢肌纤维（S1和S2）。所有F纤维都具有两种副肌球蛋白同工型（P1和P2），而除了招潮蟹的大爪外，所有慢肌纤维仅含有P2变体。S1和S2纤维通过肌钙蛋白-T的一种大型同工型（T1；Mr = 55,000）的分布来区分；所有三个物种的S2纤维除了通常与S1纤维相关的一两种较小分子量的变体之外，还含有T1。为了确定慢肌纤维在组织化学性质上是否存在差异，对地蟹爪的闭肌进行了冷冻切片，并对肌原纤维ATP酶和NADH黄递酶活性进行了染色。大多数S2纤维的ATP酶活性低于S1纤维，而NADH黄递酶活性高于S1纤维，这表明S2纤维的收缩速率较低，并且比S1纤维更耐疲劳。有人提出，通过生化和组织化学标准定义的S1和S2纤维分别与生理上特征化的慢肌纤维和紧张性纤维相同。
