The asp‐rich region at the carboxyl‐terminus of calsequestrin binds to Ca2+ and interacts with triadin

[摘要]

Calsequestrin (CSQ) is a high capacity Ca²⁺ binding protein in the junctional sarcoplasmic reticulum of striated muscles, and has been shown to regulate the ryanodine receptor (RyR) through triadin and junctin. In order to identify the functional roles of specific regions on CSQ, several CSQ deletion mutants were prepared by molecular cloning and Escherichia coli expression. ⁴⁵Ca²⁺ overlay assay using a native gel system revealed that the major Ca²⁺ binding motif of CSQ resides in the asp-rich region (amino acids 354–367). In an in vitro binding assay using a glutathione-S-transferase affinity column, the interaction between CSQ and triadin was found to be Ca²⁺-dependent, and the site of interaction was confined to the asp-rich region of CSQ. Our results suggest that the asp-rich region of CSQ could participate in the RyR-mediated Ca²⁺ release process by offering a direct binding site to luminal Ca²⁺ as well as triadin.

[学科分类] 生物化学/生物物理