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Posttranslational modification of human alphaA-crystallin: correlation with electrophoretic migration
Christine Colvis1, Donita Garland
1Laboratory of Mechanisms of Ocular Diseases, National Eye Institute, Bethesda, Maryland 20892, USA.
Archives of Biochemistry and Biophysics
|February 14, 2002
Summary
Posttranslational modifications of alphaA-crystallin in the human lens change with cell age and depth. These modifications, including phosphorylation and truncation, impact protein migration and lens structure.
Area of Science:
- Biochemistry
- Ophthalmology
- Proteomics
Background:
- AlphaA-crystallin is a key structural protein in the human lens.
- This protein undergoes various posttranslational modifications.
- Understanding these modifications is crucial for lens biology.
Purpose of the Study:
- To investigate the temporal and spatial patterns of alphaA-crystallin posttranslational modifications.
- To correlate modified protein forms with their electrophoretic migration.
- To identify specific modifications and their locations within the human lens.
Main Methods:
- Human lenses were dissected into concentric fiber cell layers.
- Proteins were separated using two-dimensional electrophoresis.
- Modified protein forms were identified and characterized by mass spectrometry.
Main Results:
- AlphaA-crystallin exhibited over 20 modified forms beyond the major spot.
- Modification extent correlated with fiber cell age and lens depth.
- Modified forms showed acidic or basic electrophoretic shifts, indicating phosphorylation, acetylation, deamidation, or truncation.
Conclusions:
- Posttranslational modifications of alphaA-crystallin are age- and depth-dependent within the human lens.
- These modifications alter protein charge and can lead to C-terminal truncation.
- Identified cleavage sites suggest similarities between alphaA- and alphaB-crystallin processing.