Gene duplication and separation of functions in αB-crystallin from zebrafish (Danio rerio)

Amber A. Smith, Keith Wyatt, Jennifer Vacha, Thomas S. Vihtelic, J. S. Zigler, Graeme J. Wistow, Mason Posner

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)481-490
Number of pages10
JournalFEBS Journal
Issue number3
StatePublished - Feb 2006
Externally publishedYes


  • Crystallins
  • Heat shock proteins
  • Lens
  • Molecular chaperones
  • Zebrafish

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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