title: Peptide scanning-based identification of regions of gamma-II crystallin involved in thermal aggregation: evidence of the involvement of structurally analogous, helix-containing loops from the two double Greek key domains of the molecule.
abstract: Gamma crystallin is one of three structural proteins present in great abundance in the fiber cells of the vertebrate eye lens. The protein displays a tendency to aggregate readily in the course of heating, cooling, being exposed to ultraviolet radiation, or rapid refolding. To investigate the molecular mechanisms underlying such aggregation, we have employed a peptide-scanning approach aimed at identifying regions of bovine gamma-II crystallin that may be involved in intermolecular interactions leading to aggregation, using assays that measure the competitive inhibition of such aggregation by reagents drawn from a group of contiguous (overlapping) peptides derived from the sequence of the protein itself. Our results suggest that two regions, comprising residues 61-74, and 145-159, play key roles in aggregative interactions. Intriguingly, the two regions (each containing a solvent-exposed, single-turn helix in the native structure) are located in structurally analogous positions in the two homologous double Greek key (beta sheet) domains of the protein, suggesting that helix-strand conversions may operate to facilitate intermolecular beta sheet interactions during aggregation.
authors.affiliation: Institute of Microbial Technology, Sector 39-A, Chandigarh 160 036, India.
authors.forename: Bishwajit
authors.initials: B
authors.lastname: Kundu
authors.forename: Anshuman
authors.initials: A
authors.lastname: Shukla
authors.forename: Purnananda
authors.initials: P
authors.lastname: Guptasarma
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001671:Biochemistry / Q000379:methods*; D002417:Cattle; D006358:Hot Temperature; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D015203:Reproducibility of Results; D012995:Solubility; D040681:Structural Homology, Protein; D013696:Temperature; D038222:gamma-Crystallins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D020033:Protein Isoforms; D038222:gamma-Crystallins