Biodiversity of the localization of the epitopes to connectin antibodies in the sarcomeres of lamprey, electric ray, and horse mackerel skeletal muscles.

SDS gel electrophoresis showed the presence of connectin, approximately 3000 kDa, in skeletal muscles of fishes, lamprey, electric ray and horse mackerel. The antibodies to avian or mammalian skeletal muscle connectin, 3B9 and Pc1200, reacted with all the fish connectins. However, a monoclonal antibody SM1 recognized electric ray connectin but did not react with lamprey and horse mackerel connectins. Immunoelectron microscopy revealed that the epitope to Pc1200 was localized at the periphery of the Z line of all the fish muscle sarcomeres and that to SM1 was located at the N2 line in the I band of ray muscle. These two localizations are the same as those in rabbit, chicken and frog skeletal muscles. On the other hand, the positions of epitopes to 3B9 were variable in the three classes of fishes, although all of them were localized in the A band. Some of the epitope positions were common to those in chicken skeletal muscle. Thus the present work demonstrates biodiversity of connectin in fish skeletal muscles, distinct from avian and mammalian skeletal muscles.