title: Predicted secondary and tertiary structures of carp gamma-crystallins with high methionine content: role of methionine residues in the protein stability.
abstract: A systematic structural comparison of several carp gamma-crystallins with high methionine contents was made by the secondary-structure prediction together with computer model-building based on the established X-ray structure of calf gamma-II crystallin. The overall surface hydrophilicity profile and the distribution of helices, beta-sheets, and beta-turns along the polypeptide chains are very similar among these carp gamma-crystallins. In addition, their general polypeptide packing is close to the characteristic 2 domain/4 motif Greek key three-dimensional conformation depicted for the calf gamma-II crystallin. Interestingly, most hydrophobic methionine residues are located on the protein surface with only a few buried inside the protein surface or in the interface between two motifs of each domain. The exposed hydrophobic and polarizable methionine cluster on the protein surface may have a bearing on the crystallin stability and dense packing in the piscine species, and probably also provides a malleable nonpolar surface for the interaction with other crystallin components for the maintenance of a clear and transparent lens.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China.
authors.forename: Y C
authors.initials: YC
authors.lastname: Liaw
authors.forename: S H
authors.initials: SH
authors.lastname: Chiou
authors.forename: T
authors.initials: T
authors.lastname: Chang
authors.forename: W C
authors.initials: WC
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002347:Carps; D003198:Computer Simulation; D003459:Crystallins / Q000737:chemistry* / Q000648:ultrastructure; D004355:Drug Stability; D008715:Methionine / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014961:X-Ray Diffraction
chemical_list: D003459:Crystallins; D008715:Methionine