Relationships among ryanodine receptor isoforms expressed in vertebrate skeletal muscles based on immunologic cross-reactivities.

To clarify the relationship among ryanodine receptor isoforms from skeletal muscles of various vertebrates (alpha- and beta-isoforms with smaller and larger mobilities on SDS-polyacrylamide gel electrophoresis, respectively), we examined the cross-reactivities of those receptors from 13 animal species by Western blot analysis, using specific polyclonal antibodies raised in rabbit against the bullfrog alpha- and beta-isoforms. Anti-beta-isoform antibody showed positive reactions against skeletal muscles from carp, five species of frogs, two species of toads, and chicken, but it was negative with four mammals. Positive reactions with anti-alpha-isoform antibody, by contrast, were limited to four species of frog Rana, although the alpha-isoforms from toads (Xenopus and Bufo) also reacted very weakly. The beta-isoforms from various animal species showed almost the same mobilities on SDS-PAGE in contrast to the variable mobilities of the alpha-isoforms. These results indicate that the beta-isoform in one animal species corresponds to the beta-isoform in other species and that the beta-isoforms are highly conserved. It is also suggested that the alpha-isoforms may be related to each other, although they are more diversified.