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The congenital cataract-linked G61C mutation destabilizes γD-crystallin and promotes non-native aggregation.

Zhang W, Cai HC, Li FF, Xi YB, Ma X, Yan YB - PLoS ONE (2011)

Bottom Line: The stability of γD-crystallin against heat- or GdnHCl-induced denaturation was significantly decreased by the mutation, while no influence was observed on the acid-induced unfolding.The aggregation-prone property of the mutant was not altered by the addition of reductive reagent.These results suggested that the decrease in protein stability followed by aggregation-prone property might be the major cause in the hereditary cataract induced by the G61C mutation.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China.

ABSTRACT
γD-crystallin is one of the major structural proteins in human eye lens. The solubility and stability of γD-crystallin play a crucial role in maintaining the optical properties of the lens during the life span of an individual. Previous study has shown that the inherited mutation G61C results in autosomal dominant congenital cataract. In this research, we studied the effects of the G61C mutation on γD-crystallin structure, stability and aggregation via biophysical methods. CD, intrinsic and extrinsic fluorescence spectroscopy indicated that the G61C mutation did not affect the native structure of γD-crystallin. The stability of γD-crystallin against heat- or GdnHCl-induced denaturation was significantly decreased by the mutation, while no influence was observed on the acid-induced unfolding. The mutation mainly affected the transition from the native state to the intermediate but not that from the intermediate to the unfolded or aggregated states. At high temperatures, both proteins were able to form aggregates, and the aggregation of the mutant was much more serious than the wild type protein at the same temperature. At body temperature and acidic conditions, the mutant was more prone to form amyloid-like fibrils. The aggregation-prone property of the mutant was not altered by the addition of reductive reagent. These results suggested that the decrease in protein stability followed by aggregation-prone property might be the major cause in the hereditary cataract induced by the G61C mutation.

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Related in: MedlinePlus

Effect of the G61C mutation on the acid-induced unfolding of γD-crystallin evaluated by the Emax value of the intrinsic fluorescence (A) and the intensity at 470 nm of the ANS fluorescence (B).
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pone-0020564-g007: Effect of the G61C mutation on the acid-induced unfolding of γD-crystallin evaluated by the Emax value of the intrinsic fluorescence (A) and the intensity at 470 nm of the ANS fluorescence (B).

Mentions: Acidosis is a frequently encountered stress in bodies. The acid resistance of the WT and mutated γD-crystallin was evaluated by measuring the structural changes when decreasing the pH of the solutions. No significant changes in either the secondary or tertiary structures were observed for both proteins as reflected by the almost constant CD signal (data not shown) and intrinsic Trp fluorescence (Figure 7). An increase in the ANS fluorescence was observed for both proteins at pH below 3.5. However, the mutation did not significantly affect the transition curve from ANS fluorescence. These results indicated that the mutation did not alter the acid-resistant property of γD-crystallin.


The congenital cataract-linked G61C mutation destabilizes γD-crystallin and promotes non-native aggregation.

Zhang W, Cai HC, Li FF, Xi YB, Ma X, Yan YB - PLoS ONE (2011)

Effect of the G61C mutation on the acid-induced unfolding of γD-crystallin evaluated by the Emax value of the intrinsic fluorescence (A) and the intensity at 470 nm of the ANS fluorescence (B).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105094&req=5

pone-0020564-g007: Effect of the G61C mutation on the acid-induced unfolding of γD-crystallin evaluated by the Emax value of the intrinsic fluorescence (A) and the intensity at 470 nm of the ANS fluorescence (B).
Mentions: Acidosis is a frequently encountered stress in bodies. The acid resistance of the WT and mutated γD-crystallin was evaluated by measuring the structural changes when decreasing the pH of the solutions. No significant changes in either the secondary or tertiary structures were observed for both proteins as reflected by the almost constant CD signal (data not shown) and intrinsic Trp fluorescence (Figure 7). An increase in the ANS fluorescence was observed for both proteins at pH below 3.5. However, the mutation did not significantly affect the transition curve from ANS fluorescence. These results indicated that the mutation did not alter the acid-resistant property of γD-crystallin.

Bottom Line: The stability of γD-crystallin against heat- or GdnHCl-induced denaturation was significantly decreased by the mutation, while no influence was observed on the acid-induced unfolding.The aggregation-prone property of the mutant was not altered by the addition of reductive reagent.These results suggested that the decrease in protein stability followed by aggregation-prone property might be the major cause in the hereditary cataract induced by the G61C mutation.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China.

ABSTRACT
γD-crystallin is one of the major structural proteins in human eye lens. The solubility and stability of γD-crystallin play a crucial role in maintaining the optical properties of the lens during the life span of an individual. Previous study has shown that the inherited mutation G61C results in autosomal dominant congenital cataract. In this research, we studied the effects of the G61C mutation on γD-crystallin structure, stability and aggregation via biophysical methods. CD, intrinsic and extrinsic fluorescence spectroscopy indicated that the G61C mutation did not affect the native structure of γD-crystallin. The stability of γD-crystallin against heat- or GdnHCl-induced denaturation was significantly decreased by the mutation, while no influence was observed on the acid-induced unfolding. The mutation mainly affected the transition from the native state to the intermediate but not that from the intermediate to the unfolded or aggregated states. At high temperatures, both proteins were able to form aggregates, and the aggregation of the mutant was much more serious than the wild type protein at the same temperature. At body temperature and acidic conditions, the mutant was more prone to form amyloid-like fibrils. The aggregation-prone property of the mutant was not altered by the addition of reductive reagent. These results suggested that the decrease in protein stability followed by aggregation-prone property might be the major cause in the hereditary cataract induced by the G61C mutation.

Show MeSH
Related in: MedlinePlus