Subnanometer-Resolution Electron Cryomicroscopy-Based Domain Models for the Cytoplasmic Region of Skeletal Muscle RyR Channel

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-07, Vol.105 (28), p.9610-9615
• Main Authors: Serysheva, Irina I., Ludtke, Steven J., Baker, Matthew L., Cong, Yao, Topf, Maya, Eramian, David, Sali, Andrej, Hamilton, Susan L., Chiu, Wah
• Format: Article
• Language: English
• Subjects: Allosteric regulation; Amino acids; Biological Sciences; Calcium; Cells; Connected regions; Cryoelectron Microscopy; Crystal structure; Cytoplasm; Membranes; Modeling; Models, Molecular; Molecular structure; Muscle, Skeletal - chemistry; Musculoskeletal system; Mutation; Protein Structure, Secondary; Protein Structure, Tertiary; Receptors; Ryanodine Receptor Calcium Release Channel - chemistry; Sarcoplasmic reticulum; Skeletal muscle; Three dimensional modeling
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0803189105

The skeletal muscle Ca²⁺ release channel (RyR1), a homotetramer, regulates the release of Ca²⁺ from the sarcoplasmic reticulum to initiate muscle contraction. In this work, we have delineated the RyR1 monomer boundaries in a subnanometer-resolution electron cryomicroscopy (cryo-EM) density map. In the cytoplasmic region of each RyR1 monomer, 36 α-helices and 7 β-sheets can be resolved. A β-sheet was also identified close to the membrane-spanning region that resembles the cytoplasmic pore structures of inward rectifier K⁺ channels. Three structural folds, generated for amino acids 12-565 using comparative modeling and cryo-EM density fitting, localize close to regions implicated in communication with the voltage sensor in the transverse tubules. Eleven of the 15 disease-related residues for these domains are mapped to the surface of these models. Four disease-related residues are found in a basin at the interfaces of these regions, creating a pocket in which the immunophilin FKBP12 can fit. Taken together, these results provide a structural context for both channel gating and the consequences of certain malignant hyperthermia and central core disease-associated mutations in RyR1.