Structural determination of the phosphorylation domain of the ryanodine receptor

The ryanodine receptor (RyR) is a large, homotetrameric sarcoplasmic reticulum membrane protein that is essential for Ca2+ cycling in both skeletal and cardiac muscle. Genetic mutations in RyR1 are associated with severe conditions including malignant hyperthermia (MH) and central core disease. One phosphorylation site (Ser 2843) has been identified in a segment of RyR1 flanked by two RyR motifs, which are found exclusively in all RyR isoforms as closely associated tandem (or paired) motifs, and are named after the protein itself. These motifs also contain six known MH mutations. In this study, we designed, expressed and purified the tandem RyR motifs, and show that this domain contains a putative binding site for the Ca2+/calmodulin-dependent protein kinase β isoform. We present a 2.2 A resolution crystal structure of the RyR domain revealing a two-fold, symmetric, extended four-helix bundle stabilized by a β sheet. Using mathematical modelling, we fit our crystal structure within a tetrameric electron microscopy (EM) structure of native RyR1, and propose that this domain is localized in the RyR clamp region, which is absent in its cousin protein inositol 1,4,5-trisphosphate receptor. Database The crystal structure of the RyR1 phosphorylation domain (amino acid residues 2734–2940) has been submitted to the Protein Data Bank under accession number 3RQR. Structured digital abstract RyR1 C3 physically interacts with CaMKIIβ by pull down (View interaction) RyR1 C3 binds to CaMKIIβ by pull down (View interaction) CaMKIIβ physically interacts with RyR1 C3 by anti tag coimmunoprecipitation (View Interaction: 1, 2)