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Publication Abstract from PubMed

Calsequestrin, the major calcium-storage protein of both cardiac and skeletal muscle, binds large amounts of Ca2+ in the sarcoplasmic reticulum and releases them during muscle contraction. For the first time, crystal structures of Ca2+-complexes for both human (hCASQ1) and rabbit skeletal calsequestrin (rCASQ1) were determined, clearly defining its Ca2+-sequestration capabilities through resolution of high- and low-affinity Ca2+-binding sites. rCASQ1 crystallized in low CaCl2 buffer revealed 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 showed fifteen Ca2+ ions, which included the six Ca2+ ions in rCASQ1. Most of the low-affinity sites, some of which were mu-carboxylate-bridged, were established by the rotation of dimeric interfaces, indicating cooperative Ca2+-binding that is consistent with our atomic absorption spectroscopic data. Based on 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.

High-capacity Ca2+-binding of human skeletal calsequestrin.,Sanchez EJ, Lewis KM, Danna BR, Kang C J Biol Chem. 2012 Feb 15. PMID:22337878^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.