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Conserved F84 and P86 residues in αB‐crystallin are essential to effectively prevent the aggregation of substrate proteins
Author(s) -
Santhoshkumar Puttur,
Sharma K. Krishna
Publication year - 2006
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.062338206
Subject(s) - crystallin , chemistry , mutant , tryptophan , chaperone (clinical) , förster resonance energy transfer , biochemistry , residue (chemistry) , cysteine , amino acid , biophysics , protein aggregation , peptide sequence , fluorescence , biology , enzyme , gene , medicine , physics , pathology , quantum mechanics
Abstract Previously, we have shown that residues 73–92 (sequence DRFSVNLDVKHFSPEELKVK) in αB‐crystallin are involved in preventing the formation of light scattering aggregates by substrate proteins. In this study, we made single substitutions of three conserved amino acid residues (H83 → A, F84 → G, and P86 → A) and a nonconserved amino acid residue (K90 → C) in the functional region of αB‐crystallin and evaluated their role in anti‐aggregation activity. Mutation of conserved residues led to changes in intrinsic tryptophan intensity, bis‐ANS binding, and in the secondary and tertiary structures. The H83A mutation led to a twofold increase in molar mass, while the other mutants did not produce significant changes in the molar mass when compared to that of wild‐type protein. The chaperone‐like activity of the H83A mutant was enhanced by 15%–20%, and the chaperone‐like activity of F84G and P86A mutants was reduced by 50%–65% when compared to the chaperone‐like activity of wild‐type αB‐crystallin. The substitution of the nonconserved residue (K90 → C) did not induce an appreciable change in the structure and function of the mutant protein. Fluorescence resonance energy transfer (FRET) assay demonstrated that destabilized ADH interacted near the K90 region in αB‐crystallin. The data show that F84 and P86 residues are essential for αB‐crystallin to effectively prevent the aggregation of substrate proteins. This study further supports the involvement of the residues in the 73–92 region of αB‐crystallin in substrate protein binding and chaperone‐like action.