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Calcium-free rat alpha-parvalbumin
Structural highlights
FunctionPRVA_RAT In muscle, parvalbumin is thought to be involved in relaxation after contraction. It binds two calcium ions. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMammals express two parvalbumins-an alpha isoform and a beta isoform. In rat, the alpha-parvalbumin (alpha-PV) exhibits superior divalent ion affinity. For example, the standard free energies for Ca2+ binding differ by 5.5 kcal/mol in 0.15 M KCl (pH 7.4). High-resolution structures of the Ca2+-bound proteins provide little insight into this disparity, prompting a structural analysis of the apo-proteins. A recent analysis of rat beta-PV suggested that Ca2+ removal provokes substantial conformational changes-reorientation of the C, D, and E helices; reorganization of the hydrophobic core; reduced interdomain contact; and remodeling of the AB domain. The energetic penalty attendant to reversing these changes, it was suggested, could contribute to the attenuated divalent ion-binding signature of that protein. That hypothesis is supported by data presented herein, describing the solution structure and peptide backbone dynamics of Ca2+-free rat alpha-PV. In marked contrast to rat beta-PV, the apo- and Ca2+-loaded forms of the rat alpha isoform are quite similar. Significant structural differences appear to be confined to the loop regions of the molecule. This finding implies that the alpha-PV isoform enjoys elevated divalent ion affinity because the metal ion-binding events do not require major structural rearrangement and the concomitant sacrifice of binding energy. Solution structure of Ca2+-free rat alpha-parvalbumin.,Henzl MT, Tanner JJ Protein Sci. 2008 Mar;17(3):431-8. Epub 2008 Jan 24. PMID:18218708[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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