POSNER, Mason; SMITH, Amber; ADAMS, Jeff; KISS, Andor J; CHENG, Chi-Hing C; Ashland University, OH; Ashland University, OH; Ashland University, OH; University of Illinois at Urbana-Champaign; University of Illinois at Urbana-Champaign: Possible thermal adaptation in the small heat shock protein &alpha A crystallin from Antarctic, temperate and tropical bony fish species
The small heat shock protein &alpha A crystallin contributes to the refractive power of the vertebrate eye lens necessary to focus light on the retina and prevents lens opacities by inhibiting the stressed-induced aggregation of other lens proteins. We previously showed that this chaperone like-activity of zebrafish and human &alpha A crystallin appears to be adapted to each species’ specific physiological temperature. In this study we further tested the hypothesis that &alpha A crystallin chaperone-like activity adapts to physiological temperature by assaying orthologous &alpha A crystallins from the cold-bodied stenothermal Antarctic toothfish, Dissostichus mawsoni, and the temperate eurythermal blunt-nose minnow, Pimephales notatus. We found that at 20° C the toothfish and minnow crystallins showed stronger chaperone-like activity than the zebrafish orthologue in preventing the DTT induced aggregation of lactalbumin. As temperature increased towards 35° C, the zebrafish protein showed increasing protection, while the toothfish showed decreasing protection. The eurythermal minnow showed strong chaperone-like activity throughout this temperature range. These data suggest that toothfish &alpha A crystallin structure is adapted to bind denaturing protein at temperatures lower than the tropical zebrafish, and that the minnow orthologue is adapted to function in a wide range of temperatures. Analysis of additional species will allow us to identify amino acid substitutions that lead to modifications in chaperone-like activity. These data will further the understanding of how &alpha A crystallin helps maintain transparency of the vertebrate lens.
