期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 287, 期 14, 页码 11592-11601出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M111.335075
关键词
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资金
- American Heart Association [850084Z]
- National Science Foundations [MCB 1021148, DBI 0959778]
- M. J. Murdock Charitable Trust
- Direct For Biological Sciences
- Div Of Biological Infrastructure [0959778] Funding Source: National Science Foundation
Calsequestrin, the major calcium storage protein in both cardiac and skeletal muscle, binds large amounts of Ca2+ in the sarcoplasmic reticulum and releases them during muscle contraction. For the first time, the crystal structures of Ca2+ complexes for both human (hCASQ1) and rabbit (rCASQ1) skeletal calsequestrin were determined, clearly defining their Ca2+ sequestration capabilities through resolution of high- and low-affinity Ca2+-binding sites. rCASQ1 crystallized in low CaCl2 buffer reveals three high-affinity Ca2+ sites with trigonal bipyramidal, octahedral, and pentagonal bipyramidal coordination geometries, along with three low-affinity Ca2+ sites. hCASQ1 crystallized in high CaCl2 shows 15 Ca2+ ions, including the six Ca2+ ions in rCASQ1. Most of the low-affinity sites, some of which are mu-carboxylate-bridged, are established by the rotation of dimer interfaces, indicating cooperative Ca2+ binding that is consistent with our atomic absorption spectroscopic data. On the basis of these findings, we propose a mechanism for the observed in vitro and in vivo dynamic high-capacity and low-affinity Ca2+-binding activity of calsequestrin.
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