title: Crystal structure of type I ryanodine receptor amino-terminal beta-trefoil domain reveals a disease-associated mutation "hot spot" loop.
abstract: Muscle contraction and relaxation is regulated by transient elevations of myoplasmic Ca(2+). Ca(2+) is released from stores in the lumen of the sarco(endo)plasmic reticulum (SER) to initiate formation of the Ca(2+) transient by activation of a class of Ca(2+) release channels referred to as ryanodine receptors (RyRs) and is pumped back into the SER lumen by Ca(2+)-ATPases (SERCAs) to terminate the Ca(2+) transient. Mutations in the type 1 ryanodine receptor gene, RYR1, are associated with 2 skeletal muscle disorders, malignant hyperthermia (MH), and central core disease (CCD). The evaluation of proposed mechanisms by which RyR1 mutations cause MH and CCD is hindered by the lack of high-resolution structural information. Here, we report the crystal structure of the N-terminal 210 residues of RyR1 (RyR(NTD)) at 2.5 A. The RyR(NTD) structure is similar to that of the suppressor domain of type 1 inositol 1,4,5-trisphosphate receptor (IP(3)Rsup), but lacks most of the long helix-turn-helix segment of the "arm" domain in IP(3)Rsup. The N-terminal beta-trefoil fold, found in both RyR and IP(3)R, is likely to play a critical role in regulatory mechanisms in this channel family. A disease-associated mutation "hot spot" loop was identified between strands 8 and 9 in a highly basic region of RyR1. Biophysical studies showed that 3 MH-associated mutations (C36R, R164C, and R178C) do not adversely affect the global stability or fold of RyR(NTD), supporting previously described mechanisms whereby mutations perturb protein-protein interactions.
authors.affiliation: Division of Signaling Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON, Canada M5G 1L7.
authors.forename: Fernando J
authors.initials: FJ
authors.lastname: Amador
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.forename: Noboru
authors.initials: N
authors.lastname: Ishiyama
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Plevin
authors.forename: Aaron
authors.initials: A
authors.lastname: Wilson
authors.forename: David H
authors.initials: DH
authors.lastname: MacLennan
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Ikura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019571:Arrhythmogenic Right Ventricular Dysplasia / Q000235:genetics; D018360:Crystallography, X-Ray; D004194:Disease / Q000235:genetics*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000737:chemistry; D008305:Malignant Hyperthermia / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry; D009154:Mutation / Q000235:genetics*; D020512:Myopathy, Central Core / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry*; D012996:Solutions
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D050505:Mutant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D012996:Solutions