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Age-dependent deamidation of alpha B-crystallin
P J Groenen1, M J van Dongen, C E Voorter
1Department of Biochemistry, University of Nijmegen, The Netherlands.
FEBS Letters
|May 3, 1993
Summary
Aging causes deamidation in bovine alpha B-crystallin at Asn-146. This process, though slow in vivo, involves succinimide intermediates and racemization in vitro, impacting lens protein stability.
Area of Science:
- Biochemistry
- Protein Chemistry
- Ocular Biochemistry
Background:
- Alpha B-crystallin is a major structural protein in the eye lens, crucial for maintaining lens transparency.
- Protein aging, including deamidation, is associated with age-related ocular diseases and changes in lens properties.
Purpose of the Study:
- To identify the specific site of deamidation in bovine alpha B-crystallin during aging.
- To investigate the mechanism and kinetics of deamidation in bovine alpha B-crystallin.
Main Methods:
- Peptide mapping following tryptic digestion of aged bovine alpha B-crystallin.
- Analysis of asparagine residue modification using mass spectrometry or advanced sequencing techniques.
- In vitro deamidation studies to assess reaction intermediates and kinetics.
Main Results:
- Deamidation was specifically identified at asparagine residue 146 (Asn-146) in bovine alpha B-crystallin.
- The other asparagine residue (Asn-78) was not found to be deamidated.
- In vitro studies demonstrated that deamidation proceeds via a succinimide intermediate, accompanied by significant racemization.
Conclusions:
- Asn-146 is the primary site of deamidation in bovine alpha B-crystallin during aging.
- The deamidation mechanism involves succinimide formation, suggesting potential implications for protein structure and function.
- The low in vivo deamidation rate despite favorable flanking residues warrants further investigation into regulatory factors.