Functional validation of hydrophobic adaptation to physiological temperature in the small heat shock protein αA-crystallin

• Published in: PloS one Vol. 7; no. 3; p. e34438
• Main Authors: Posner, Mason, Kiss, Andor J, Skiba, Jackie, Drossman, Amy, Dolinska, Monika B, Hejtmancik, J Fielding, Sergeev, Yuri V
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 29.03.2012; Public Library of Science (PLoS)
• Subjects: Acclimatization; Acids; Adaptation; Agglomeration; alpha-Crystallin A Chain - chemistry; alpha-Crystallin A Chain - genetics; alpha-Crystallin A Chain - metabolism; Amino Acid Sequence; Amino acids; Animals; Bioinformatics; Biology; Correlation; Crystal structure; Crystallin; Crystallinity; Cytochrome; Danio rerio; Evolutionary biology; Fishes; Heat shock proteins; Heat-Shock Proteins, Small - chemistry; Heat-Shock Proteins, Small - genetics; Heat-Shock Proteins, Small - metabolism; Homeostasis; Hydrophobic and Hydrophilic Interactions; Hydrophobicity; Mammals; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Phylogenetics; Physiology; Protein Conformation; Protein interaction; Protein Stability; Protein structure; Proteins; Quaternary structure; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Sequence Alignment; Site-directed mutagenesis; Small heat shock proteins; Stability analysis; Structural stability; Studies; Temperature; Zebrafish; United States > US; Maryland; Ohio
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0034438

Small heat shock proteins (sHsps) maintain cellular homeostasis by preventing stress and disease-induced protein aggregation. While it is known that hydrophobicity impacts the ability of sHsps to bind aggregation-prone denaturing proteins, the complex quaternary structure of globular sHsps has made understanding the significance of specific changes in hydrophobicity difficult. Here we used recombinant protein of the lenticular sHsp α A-crystallin from six teleost fishes environmentally adapted to temperatures ranging from -2°C to 40°C to identify correlations between physiological temperature, protein stability and chaperone-like activity. Using sequence and structural modeling analysis we identified specific amino acid differences between the warm adapted zebrafish and cold adapted Antarctic toothfish that could contribute to these correlations and validated the functional consequences of three specific hydrophobicity-altering amino acid substitutions in αA-crystallin. Site directed mutagenesis of three residues in the zebrafish (V62T, C143S, T147V) confirmed that each impacts either protein stability or chaperone-like activity or both, with the V62T substitution having the greatest impact. Our results indicate a role for changing hydrophobicity in the thermal adaptation of α A-crystallin and suggest ways to produce sHsp variants with altered chaperone-like activity. These data also demonstrate that a comparative approach can provide new information about sHsp function and evolution.