BIOT 480 |
| Human γC crystallin (HγC-Crys) is a major protein of the lens nucleus. Aggregated and oxidatively damaged forms are recovered from the insoluble fraction of nuclear cataracts. HγC-Crys is a two domain all β-sheet monomer, homologous to γD- and γS-crystallins. Mutations in the genes encoding these proteins are associated with juvenile-onset cataracts[1]. Equilibrium unfolding and refolding experiments at pH 7, 37°C, revealed that wild-type HγC-Crys exhibited a transition midpoint of 2.7M GuHCl. The transition was reversible above 1.0 M GuHCl. An aggregation pathway competed with productive refolding at near physiological conditions, with denaturant concentrations below 1.0M GuHCl. Similar aggregation observed in HγD-Crys were previously observed to have branched fibril structure using AFM[2]. When incubated without denaturant at pH 3 and 37°C, HγC-Crys assembled into non-branched fibril structures in vitro. Characterization by dye binding assays, polarized microscopy, and transmission electron microscopy showed that these non-branched species have characteristics of fibrils associated with amyloid diseases. The formation of HγC-Crys fibrils under destabilizing conditions may be significant for the development of cataract with aging. 1. Liang, J.J., Interactions and Chaperone Function of αA-Crystallin with T5P γC-Crystallin Mutant. Protein Sci, 2004. 13(9): 2476-82. 2. Kosinski-Collins, M.S. and King, J., In Vitro Unfolding, Refolding, and Polymerization of Human γD Crystallin, a Protein Involved in Cataract Formation. Protein Sci, 2003. 12(3): 480-90. |
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Biophysical and Biomolecular Symposium: Protein Aggregation
2:00 PM-5:25 PM, Thursday, August 23, 2007 BCEC -- 107C, Oral
Division of Biochemical Technology |