IDENTIFICATION OF 2 RYANODINE RECEPTOR TRANSCRIPTS IN NEONATAL, SLOW-TWITCH, AND FAST-TWITCH RABBIT SKELETAL-MUSCLES

Analysis of the primary structure of the rabbit skeletal muscle ryanod ine receptor led to the identification of two molecules of 5032 and 50 37 residues, respectively. Such a sequence discrepancy is likely to be due to the alternative splicing of a 15 bp exon (1) encoding a 5 amin o acid insertion (Ala-Gly-Asp-Ala-Gln) after residue 3479. By using PC R on first strand cDNA, we searched for the 15 base pair insertion in the ryanodine receptor mRNA from adult slow- and fast-twitch skeletal muscle, as well as from fast-muscles, at various stages of post-natal development. All rabbit skeletal muscle mRNAs, regardless of their dev elopmental stage and twitch properties, contain two RYR transcripts, s uggesting the coexistence of two RYR isoforms in mammalian skeletal mu scle. (C) 1994 Academic Press, Inc.