کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2185670 1096000 2010 19 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Partially Folded Aggregation Intermediates of Human γD-, γC-, and γS-Crystallin Are Recognized and Bound by Human αB-Crystallin Chaperone
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی بیولوژی سلول
پیش نمایش صفحه اول مقاله
Partially Folded Aggregation Intermediates of Human γD-, γC-, and γS-Crystallin Are Recognized and Bound by Human αB-Crystallin Chaperone
چکیده انگلیسی

Human γ-crystallins are long-lived, unusually stable proteins of the eye lens exhibiting duplicated, double Greek key domains. The lens also contains high concentrations of the small heat shock chaperone α-crystallin, which suppresses aggregation of model substrates in vitro. Mature-onset cataract is believed to represent an aggregated state of partially unfolded and covalently damaged crystallins. Nonetheless, the lack of cell or tissue culture for anucleate lens fibers and the insoluble state of cataract proteins have made it difficult to identify the conformation of the human γ-crystallin substrate species recognized by human α-crystallin. The three major human lens monomeric γ-crystallins, γD, γC, and γS, all refold in vitro in the absence of chaperones, on dilution from denaturant into buffer. However, off-pathway aggregation of the partially folded intermediates competes with productive refolding. Incubation with human αB-crystallin chaperone during refolding suppressed the aggregation pathways of the three human γ-crystallin proteins. The chaperone did not dissociate or refold the aggregated chains under these conditions. The αB-crystallin oligomers formed long-lived stable complexes with their γD-crystallin substrates. Using α-crystallin chaperone variants lacking tryptophans, we obtained fluorescence spectra of the chaperone–substrate complex. Binding of substrate γ-crystallins with two or three of the four buried tryptophans replaced by phenylalanines showed that the bound substrate remained in a partially folded state with neither domain native-like. These in vitro results provide support for protein unfolding/protein aggregation models for cataract, with α-crystallin suppressing aggregation of damaged or unfolded proteins through early adulthood but becoming saturated with advancing age.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Biology - Volume 401, Issue 1, 6 August 2010, Pages 134–152
نویسندگان
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