Different muscle-specific forms of rabbit skeletal muscle alpha-actinin

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Abstract
The structures and functions of the 2 .alpha.-actinin isoforms [R. Kobayashi et al. (1983)], isolated from rabbit longissimus dorsi and psoas muscles were compared. One-dimensional and 2-dimensional electrophoretic analyses showed that the 2 .alpha.-actinins were different from each other in their subunit chain weights and isoelectric points. The Stokes'' radius of the longissimus dorsi and psoas .alpha.-actinins was 7.4 nm and 7.0 nm, respectively. Although the 2 .alpha.-actinins are similar in their amino acid compositions, longissimus dorsi .alpha.-actinin apparently contains more aspartic acid and isoleucine than psoas .alpha.-actinin but fewer glycine and valine residues. Analysis of the soluble tryptic peptides by 2-dimensional mapping revealed that the 2 .alpha.-actinins had major differences. These data suggested that the 2 isoforms are the products of at least 2 different genes. Despite these differences, both .alpha.-actinins share a number of common properties. Both .alpha.-actinins contain a 55-kDA [kilodalton] peptide resistat to trypsin. The 2 proteins show no differences in actomyosin turbidity assays, ATPase assays and F-actin binding assays of .alpha.-actinin activity. Immunological examination indicates that the 2 .alpha.-actinins share antigenic determinants in common.