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Solution structures of chicken parvalbumin 3 in the Ca 2+ ‐free and Ca 2+ ‐bound states
Author(s) -
Henzl Michael T.,
Tanner John J.,
Tan Anmin
Publication year - 2011
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.22915
Subject(s) - parvalbumin , chemistry , gene isoform , crystallography , divalent , biology , biochemistry , organic chemistry , neuroscience , gene
Birds express two β‐parvalbumin isoforms, parvalbumin 3 and avian thymic hormone (ATH). Parvalbumin 3 from chicken (CPV3) is identical to rat β‐parvalbumin (β‐PV) at 75 of 108 residues. CPV3 displays intermediate Ca 2+ affinity—higher than that of rat β‐parvalbumin, but lower than that of ATH. As in rat β‐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 α‐ and β‐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 β‐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. © 2010 Wiley‐Liss, Inc.