Ryanodine receptors (RyRs) form calcium release channels located in the membranes of the sarcoplasmic and endoplasmic reticulum. RyRs play a major role in excitation-contraction coupling and other Ca2+-dependent signalling events, and consist of several globular domains that together form a large assembly. Here we describe the crystal structures of the SPRY1 and tandem-repeat domains at 1.2-1.5 Å resolution, which reveal several structural elements not detected in recent cryo-EM reconstructions of RyRs. The cryo-EM studies disagree on the position of SPRY domains, which had been proposed based on homology modelling. Computational docking of the crystal structures, combined with FRET studies, show that the SPRY1 domain is located next to FK506-binding protein (FKBP). Molecular dynamics flexible fitting and mutagenesis experiments suggest a hydrophobic cluster within SPRY1 that is crucial for FKBP binding. A RyR1 disease mutation, N760D, appears to directly impact FKBP binding through interfering with SPRY1 folding.
Bibliographical noteFunding Information:
We thank the support staff at the Advanced Photon Source (Chicago) GM/CA-CAT beamline 23-ID-D, the Stanford Synchrotron Radiation Light source (Menlo Park, USA), and at the Canadian Light Source (Saskatoon, SK, Canada), which is supported by the Natural Sciences and Engineering Research Council of Canada, the National Research Council Canada, the Canadian Institutes of Health Research (CIHR), the Province of Saskatchewan, Western Economic Diversification Canada, and the University of Saskatchewan. The trilateration software was kindly provided by Dr Bengt Svensson (firstname.lastname@example.org). This work is supported by an operating grant from the CIHR (MOP-119608, application # 259009) to F.V.P., and NIH grants R01AR059124 (to J.D.F.) and R01HL092097 (to R.L.C.).