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UV-A-induced structural and functional changes in human lens deamidated alphaB-crystallin
Kerri Mafia1, Ratna Gupta, Marion Kirk
1Department of Pharmacology, University of Alabama at Birmingham, Birmingham, AL 35226, USA.
Molecular Vision
|March 13, 2008
Summary
Ultraviolet A irradiation significantly impacts alphaB-crystallin structure and function. The alphaB-Asn146Asp mutant protein exhibits a complete loss of chaperone activity due to oxidative damage and structural alterations.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- AlphaB-crystallin is a small heat shock protein involved in cellular protection.
- Deamidation of asparagine residues can alter protein structure and function.
- Ultraviolet A (UV-A) irradiation can induce protein damage and oxidative stress.
Purpose of the Study:
- To compare the effects of UV-A irradiation on wild-type (WT) alphaB-crystallin and its deamidated mutants.
- To investigate UV-A-induced structural and functional changes in alphaB-crystallin.
- To correlate structural alterations with the loss of chaperone activity.
Main Methods:
- Recombinant WT alphaB-crystallin and three deamidated mutants (alphaB-Asn78Asp, alphaB-Asn146Asp, alphaB-Asn78/146Asp) were exposed to UV-A light.
- Chaperone activity was assessed.
- Structural properties including dimerization, degradation, tryptophan fluorescence, ANS-binding, UV-CD spectra, size exclusion chromatography, and residue oxidation were analyzed.
Main Results:
- UV-A exposure induced dimerization and degradation in all alphaB-crystallin variants.
- The alphaB-Asn146Asp mutant showed a greater loss of chaperone activity compared to WT and other mutants.
- Structural changes, including increased surface hydrophobicity and random coil structure, were most pronounced in alphaB-Asn146Asp.
- Oxidation of methionine and tryptophan residues was highest in alphaB-Asn146Asp after UV-A exposure.
Conclusions:
- The deamidated alphaB-Asn146Asp mutant protein completely lost chaperone activity after UV-A exposure.
- Oxidative damage and significant structural alterations in alphaB-Asn146Asp contribute to its functional impairment.
- UV-A irradiation differentially affects deamidated alphaB-crystallin variants, highlighting the role of specific residues in protein stability and function.