MYOFIBRILLAR PROTEINS IN SKELETAL-MUSCLES OF PARR, SMOLT AND ADULT ATLANTIC SALMON (SALMO-SALAR L) - COMPARISON WITH ANOTHER SALMONID, THE ARCTIC CHARR SALVELINUS-ALPINUS (L)

The heavy and light subunits of myosin from white and red muscles of Atlantic salmon parr, smolt and adult individuals were analyzed by SDS-PAGE and two-dimensional electrophoresis. Tropomyosin was identified by comigration with rat tropomyosins in two-dimensional gels in the presence and absence of urea. These myofibrillar proteins were compared to those of Arctic charr. 1. The myosin heavy chain from Atlantic salmon red muscles was associated with two types of light chain, IS and 2S, that comigrated with the light chains IS and 2S of Arctic charr. 2. As in the Arctic charr, four myosin light chain spots were detected in white muscles: two fast myosin light chains type 1, one of which comigrated with its analogous in the Arctic charr; one fast myosin light chain type 2, differing slightly in isoelectric point from that of Arctic charr; and one fast myosin light chain type 3 with higher electrophoretic mobility than that of Arctic charr. 3. Three tropomyosin spots were detected. White muscles contained only one type of beta-tropomyosin and red muscles two types of alpha-tropomyosin. These three tropomyosin spots comigrated with those of Arctic charr. 4. Two myosin heavy chain bands were observed in red muscles of salmon parrs but only one in the rest of the red muscles analyzed. 5. Only one myosin heavy chain band was detected in white muscles by SDS-glycerol-polyacrylamide gel electrophoresis. Alfa-chymotryptic peptide mapping of these white myosin heavy chain bands revealed differences attributed to the presence of a new type of myosin heavy chain first detected several months after smoltification.