Oligomerization of the cardiac ryanodine receptor C-terminal tail

The C-terminal 100 amino acids of the RyR (ryanodine receptor), referred to as the C-terminal tail, is a highly conserved sequence that is present in all known RyR isoforms and which has been implicated in channel function. Deleting the final 15 amino acids from the full-length skeletal muscle RyR resulted in an inactive channel, attributed to impaired assembly of a tetrameric RyR complex [Gao, Tripathy, Lu and Meissner (1997) FEBS Lett. 412, 223-226]. To account for these observations, the C-terminal tail itself may be an important molecular determinant of oligomerization. Alternatively, the large N-terminal cytoplasmic domain may fold back upon itself to interact with the C-terminal tail to provide a correctly folded tetrameric structure. We explored these possibilities for RyR2 (cardiac RyR) using the yeast two-hybrid interaction assay and in vitro translation followed by immunoprecipitation and chemical cross-linking. The data indicate that the C-terminal tail of RyR2 is capable of self-tetramerization. Moreover, a truncated C-terminal tail, lacking the final 15 amino acids, failed to self-associate. These observations suggest that the intrinsic ability of the RyR C-terminal tail to self-tetramerize may be vitally important for the oligomeric assembly of the native RyR channel.