5crh | pdb_00005crh
Human skeletal calsequestrin, M53T mutant high-calcium complex
Structural highlights
Function[CASQ1_HUMAN] Calsequestrin is a high-capacity, moderate affinity, calcium-binding protein and thus acts as an internal calcium store in muscle. Calcium ions are bound by clusters of acidic residues at the protein surface, often at the interface between subunits. Can bind around 80 Ca(2+) ions. Regulates the release of lumenal Ca(2+) via the calcium release channel RYR1; this plays an important role in triggering muscle contraction.[1] [2] Publication Abstract from PubMedCalsequestrin 1 is the principal Ca(2+) storage protein of the sarcoplasmic reticulum of skeletal muscle. Its inheritable D244G mutation causes a myopathy with vacuolar aggregates, whereas its M87T "variant" is weakly associated with malignant hyperthermia. We characterized the consequences of these mutations with studies of the human proteins in vitro. Equilibrium dialysis and turbidity measurements showed that D244G and, to a lesser extent, M87T partially lose Ca(2+) binding exhibited by wild type calsequestrin 1 at high Ca(2+) concentrations. D244G aggregates abruptly and abnormally, a property that fully explains the protein inclusions that characterize its phenotype. D244G crystallized in low Ca(2+) concentrations lacks two Ca(2+) ions normally present in wild type that weakens the hydrophobic core of Domain II. D244G crystallized in high Ca(2+) concentrations regains its missing ions and Domain II order but shows a novel dimeric interaction. The M87T mutation causes a major shift of the alpha-helix bearing the mutated residue, significantly weakening the back-to-back interface essential for tetramerization. D244G exhibited the more severe structural and biophysical property changes, which matches the different pathophysiological impacts of these mutations. Characterization of Two Human Skeletal Calsequestrin Mutants Implicated in Malignant Hyperthermia and Vacuolar Aggregate Myopathy.,Lewis KM, Ronish LA, Rios E, Kang C J Biol Chem. 2015 Nov 27;290(48):28665-74. doi: 10.1074/jbc.M115.686261. Epub, 2015 Sep 28. PMID:26416891[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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