title: Wild-type human γD-crystallin promotes aggregation of its oxidation-mimicking, misfolding-prone W42Q mutant.
abstract: Non-native protein conformers generated by mutation or chemical damage template aggregation of wild-type, undamaged polypeptides in diseases ranging from amyotrophic lateral sclerosis to cancer. We tested for such interactions in the natively monomeric human eye lens protein γd-crystallin, whose aggregation leads to cataract disease. The oxidation-mimicking W42Q mutant of γd-crystallin formed non-native polymers starting from a native-like state under physiological conditions. Aggregation occurred in the temperature range 35-45 °C, in which the mutant protein began to lose the native conformation of its N-terminal domain. Surprisingly, wild-type γd-crystallin promoted W42Q polymerization in a catalytic manner, even at mutant concentrations too low for homogeneous nucleation to occur. The presence of wild-type protein also downshifted the temperature range of W42Q aggregation. W42Q aggregation required formation of a non-native intramolecular disulfide bond but not intermolecular cross-linking. Transient WT/W42Q binding may catalyze this oxidative misfolding event in the mutant. That a more stable variant in a mixture can specifically promote aggregation of a less stable one rationalizes how extensive aggregation of rare damaged polypeptides can occur during the course of aging.
authors: From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
authors: Eugene
authors: E
authors: Serebryany
authors: From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 jaking@mit.edu.
authors: Jonathan A
authors: JA
authors: King
mesh_terms: D000595:Amino Acid Sequence; D055162:Biocatalysis; D003080:Cold Temperature; D004220:Disulfides / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D010084:Oxidation-Reduction; D017510:Protein Folding; D055503:Protein Multimerization; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D038222:gamma-Crystallins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: C504903:CRYGD protein, human; D004220:Disulfides; D038222:gamma-Crystallins
keywords: Aggregation; Cataract; Crystallin; Domain Swapping; Eye Lens; Oxidative Damage; Protein Misfolding; Protein Stability; Unfolding Intermediate; Wild-type/Mutant Interaction