title: Apocalmodulin and Ca2+-calmodulin bind to neighboring locations on the ryanodine receptor.
abstract: Calmodulin (CaM) binds to the ryanodine receptor/calcium release channel of skeletal muscle (RyR1), both in the absence and presence of Ca(2+), and regulates the activity of the channel activity by activating and inhibiting it, respectively. Using cryo-electron microscopy and three-dimensional reconstruction, we found that one apoCaM binds per RyR1 subunit along the sides of the cytoplasmic assembly of the receptor. This location is distinct from but close to the location found for Ca(2+)-CaM, providing a structural basis for efficient switching of CaM between these two positions with the oscillating intracellular Ca(2+) concentration that generates muscle relaxation/contraction cycles. The locations of apoCaM and Ca(2+)-CaM at a critical region for RYR1-dihydropyridine receptor interaction are suggestive of a direct role for CaM in the mechanism of excitation-contraction coupling.
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA. samso@wadsworth.org
authors.forename: Montserrat
authors.initials: M
authors.lastname: Samsó
authors.forename: Terence
authors.initials: T
authors.lastname: Wagenknecht
mesh_terms: D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D018482:Muscle, Skeletal / Q000502:physiology; D011485:Protein Binding; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D001059:Apoproteins; D002147:Calmodulin; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium