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Publication Abstract from PubMed

Birds express two beta-parvalbumin isoforms, parvalbumin 3 and avian thymic hormone (ATH). Parvalbumin 3 from chicken (CPV3) is identical to rat beta-parvalbumin (beta-PV) at 75 of 108 residues. CPV3 displays intermediate Ca(2+) affinity-higher than that of rat beta-parvalbumin, but lower than that of ATH. As in rat beta-PV, the attenuation of affinity is associated primarily with the CD site (residues 41-70), rather than the EF site (residues 80-108). Structural data for rat alpha- and beta-parvalbumins suggest that divalent ion affinity is correlated with the similarity of the unliganded and Ca(2+) -bound conformations. We herein present a comparison of the solution structures of Ca(2+) -free and Ca(2+) -bound CPV3. Although the structures are generally similar, the conformations of residues 47 to 50 differ markedly in the two protein forms. These residues are located in the C helix, proximal to the CD binding loop. In response to Ca(2+) removal, F47 experiences much greater solvent accessibility. The side-chain of R48 assumes a position between the C and D helices, adjacent to R69. Significantly, I49 adopts an interior position in the unliganded protein that allows association with the side-chain of L50. Concomitantly, the realignment of F66 and F70 facilitates their interaction with I49 and reduces their contact with residues in the N-terminal AB domain. This reorganization of the hydrophobic core, although less profound, is nevertheless reminiscent of that observed in rat beta-PV. The results lend further support to the idea that Ca(2+) affinity correlates with the structural similarity of the apo- and bound parvalbumin conformations. Proteins 2011. (c) 2010 Wiley-Liss, Inc.

Solution structures of chicken parvalbumin 3 in the Ca(2+) -free and Ca(2+) -bound states.,Henzl MT, Tanner JJ, Tan A Proteins. 2011 Mar;79(3):752-64. doi: 10.1002/prot.22915. Epub 2010 Dec 3. PMID:21287610^[1]

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