High‐resolution two‐dimensional electrophoresis of myofibrillar proteins with immobilized pH gradients

Abstract

Abstract Previous studies by chromatography and electrophoresis have demonstrated that myosin is composed of two classes of polypeptide chains: high relative molecular mass ( M r ) components (200 000) and a class of lower M r species, called the “light chains” (LC). It has been shown before by others that the slow‐twitching fibers contain 2 types of isoforms: LC1s and LC2s, while the fast‐twitching fibers contain 3 types: LC1f, LC3f and LC2f, the latter also existing as phosphorylated forms. In the present investigation, utilizing two‐dimensional (2‐D) maps generated with narrow immobilized pH gradients in the first dimension, a higher resolution of the myosin LC has been achieved. The LC1s chains are further fractionated into at least four isoforms; LC2s into three; LC2f into four and LC3f into three sub‐species in rabbit muscles. Skeletal muscle tropomyosin, which is separated into three forms (α s , α f and β), is here resolved into six components, while actin from skeletal muscle, previously described mainly as a single chain (α), is here sub‐fracionated into four isoforms of identical M r and different charge. The series of isoforms here reported could represent a fine probe for investigating such complex phenomena as the cellular differentiation of human satellite cells from normal and pathological subjects in greater detail than before.