Contraction of striated muscle results from a rise in cytoplasmic calcium concentration in a process termed excitation/contraction coupling. Most of this calcium moves back and forth across the sarcoplasmic-reticulum membrane in cycles of contraction and relaxation. The channel responsible for release from the sarcoplasmic reticulum is the ryanodine receptor, whereas Ca2+-ATPase effects reuptake in an ATP-dependent manner. The structures of these two molecules have been studied by cryoelectron microscopy, with helical crystals in the case of Ca2+-ATPase and as isolated tetramers in the case of ryanodine receptor. Structures of Ca2+-ATPase at 8-Angstrom resolution reveal the packing of transmembrane helices and have allowed fitting of a putative ATP-binding domain among the cytoplasmic densities. Comparison of ATPases in different conformations gives hints about the conformational changes that accompany the reaction cycle. Structures of ryanodine receptor at 30-Angstrom resolution reveal a multitude of isolated domains in the cytoplasmic portion, as well as a distinct transmembrane assembly. Binding sites for various protein ligands have been determined and conformational changes induced by ATP, calcium and ryanodine have been characterized. Both molecules appear to use large conformational changes to couple interactions in their cytoplasmic domains with calcium transport through their membrane domains, and future studies at higher resolution will focus on the mechanisms for this coupling.
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Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
Chen, SRW
;
Ebisawa, K
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Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
Ebisawa, K
;
Li, XL
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Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
Li, XL
;
Zhang, L
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Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
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Univ Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, CanadaUniv Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, Canada
Du, GG
;
MacLennan, DH
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Univ Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, CanadaUniv Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, Canada
机构:
Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
Chen, SRW
;
Ebisawa, K
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Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
Ebisawa, K
;
Li, XL
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Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
Li, XL
;
Zhang, L
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h-index: 0
机构:
Univ Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, CanadaUniv Calgary, Dept Med Biochem, Cardiovasc Res Grp, Calgary, AB T2N 4N1, Canada
机构:
Univ Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, CanadaUniv Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, Canada
Du, GG
;
MacLennan, DH
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h-index: 0
机构:
Univ Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, CanadaUniv Toronto, Banting & Best Dept Med Res, Charles H Best Inst, Toronto, ON M5G 1L6, Canada