[Back to Issue 2 ToC] [Back to Journal Contents] [Back to Biochemistry (Moscow) Home page]
[View Full Article] [Download Reprint (PDF)]

Structure, Chaperone Activity, and Aggregation of Wild-Type and R12C Mutant αB-Crystallins in the Presence of Thermal Stress and Calcium Ion – Implications for Role of Calcium in Cataract Pathogenesis

M. Ragerdi Kashani1, R. Yousefi1*, M. Akbarian1, M. M. Alavianmehr2, and Y. Ghasemi3

1Shiraz University, Protein Chemistry Laboratory (PCL), Department of Biology, 71345 Shiraz, Iran; fax: + (98) 711-32280916; E-mail: ryousefi@shirazu.ac.ir

2Shiraz University of Technology, Department of Chemistry, Shiraz, Iran

3Department of Pharmaceutical Biotechnology and Pharmaceutical Sciences Research Center, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran

* To whom correspondence should be addressed.

Received August 9, 2015; Revision received September 19, 2015
The current study was performed with the aim to evaluate the chaperoning ability, structural features, and aggregation propensity of wild-type and R12C mutant αB-crystallins (αB-Cry) under thermal stress and in the presence of calcium ion. The results of different spectroscopic analyses suggest that wild-type and mutant αB-Cry have dissimilar secondary and tertiary structures. Moreover, αB-Cry indicates slightly improved chaperone activity upon the R12C mutation. Thermal stress and calcium, respectively, enhance and reduce the extent of solvent-exposed hydrophobic surfaces accompanying formation of ordered and non-ordered aggregate entities in both proteins. Compared to the wild-type protein, the R12C mutant counterpart shows significant resistance against thermal and calcium-induced aggregation. In addition, in the presence of calcium, significant structural variation was accompanied by reduction in the solvent-exposed hydrophobic patches and attenuation of chaperone activity in both proteins. Additionally, gel mobility shift assay indicates the intrinsic propensity of R12C mutant αB-Cry for disulfide bridge-mediated protein dimerization. Overall, the results of this study are of high significance for understanding the molecular details of different factors that are involved in the pathomechanism of cataract disorders.
KEY WORDS: αB-crystallin, R12C mutation, chaperone, thermal stress, aggregation

DOI: 10.1134/S0006297916020061