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- Title
Gene duplication and separation of functions in αB-crystallin from zebrafish ( Danio rerio).
- Authors
Smith, Amber A.; Wyatt, Keith; Vacha, Jennifer; Vihtelic, Thomas S.; Zigler Jr, J. S.; Wistow, Graeme J.; Posner, Mason
- Abstract
We previously reported that zebrafish αB-crystallin is not constitutively expressed in nervous or muscular tissue and has reduced chaperone-like activity compared with its human ortholog. Here we characterize the tissue expression pattern and chaperone-like activity of a second zebrafish αB-crystallin. Expressed sequence tag analysis of adult zebrafish lens revealed the presence of a novel α-crystallin transcript designated cryab2 and the resulting protein αB2-crystallin. The deduced protein sequence was 58.2% and 50.3% identical with human αB-crystallin and zebrafish αB1-crystallin, respectively. RT-PCR showed that αB2-crystallin is expressed predominantly in lens but, reminiscent of mammalian αB-crystallin, also has lower constitutive expression in heart, brain, skeletal muscle and liver. The chaperone-like activity of purified recombinant αB2 protein was assayed by measuring its ability to prevent the chemically induced aggregation of α-lactalbumin and lysozyme. At 25 °C and 30 °C, zebrafish αB2 showed greater chaperone-like activity than human αB-crystallin, and at 35 °C and 40 °C, the human protein provided greater protection against aggregation. 2D gel electrophoresis indicated that αB2-crystallin makes up ≈ 0.16% of total zebrafish lens protein. Zebrafish is the first species known to express two different αB-crystallins. Differences in primary structure, expression and chaperone-like activity suggest that the two zebrafish αB-crystallins perform divergent physiological roles. After gene duplication, zebrafish αB2 maintained the widespread protective role also found in mammalian αB-crystallin, while zebrafish αB1 adopted a more restricted, nonchaperone role in the lens. Gene duplication may have allowed these functions to separate, providing a unique model for studying structure–function relationships and the regulation of tissue-specific expression patterns.
- Subjects
ZEBRA danio; BRACHYDANIO; HEAT shock proteins; MOLECULAR chaperones; PROTEINS; CRYSTALLINE lens; EYE
- Publication
FEBS Journal, 2006, Vol 273, Issue 3, p481
- ISSN
1742-464X
- Publication type
Article
- DOI
10.1111/j.1742-4658.2005.05080.x