epsilon-Crystallin from duck eye lens. Comparisonof its quaternary structure and stability with other lactate dehydrogenases and complex formation with alpha-crystallin

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Item Type:	Article
Title:	epsilon-Crystallin from duck eye lens. Comparisonof its quaternary structure and stability with other lactate dehydrogenases and complex formation with alpha-crystallin
Creators Name:	Berr, K., Wassenberg, D., Lilie, H., Behlke, J. and Jaenicke, R.
Abstract:	Taxon-specific {epsilon}-crystallin ({epsilon}C) from duck eye lens is identical to duck heart muscle lactate dehydrogenase. It forms a dimer of dimers with a dissociation constant of 2.2 x 10 -7 M, far beyond the value observed for other vertebrate lactate dehydrogenases. Comparing the characteristics of wild-type {epsilon}-crystallin with those of three mutants, G115N, G119F and 115N/119F, representing the only significant peripheral sequence variations between duck {epsilon}C and chicken or pig heart muscle lactate dehydrogenase, no significant conformational differences are detectable. Regarding the catalytic properties, the Michaelis constant of the double mutant 115N/119F for pyruvate is found to be decreased; for wild-type enzyme, the effect is overcompensated by the high expression level of {epsilon}C in the eye lens. As taken from spectral analysis of the guanidine-induced and temperature-induced denaturation transitions, {epsilon}C in its dimeric state is relatively unstable, whereas the native tetramer exhibits the high intrinsic stability characteristic of common vertebrate heart and muscle lactate dehydrogenases. The denaturation mechanism of {epsilon}C is complex and only partially reversible. In the case of thermal unfolding, the predominant side reaction competing with the reconstitution of the native state is the kinetic partitioning between proper folding and aggregation, {alpha}-Crystallin, the major molecular chaperone in the eye lens, inhibits the aggregation of {epsilon}C by trapping the misfolded protein.
Keywords:	Chaperone, Crystallin, Eye-Lens Proteins, Lactate Dehydrogenase, Stability
Source:	European Journal of Biochemistry
ISSN:	0014-2956
Publisher:	Blackwell Publishing
Volume:	267
Number:	17
Page Range:	5413-5420
Date:	1 January 2000
Official Publication:	https://doi.org/10.1046/j.1432-1327.2000.01598.x
PubMed:	View item in PubMed

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