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M Posner, S Low, S Runkle, J Hill, M Kantorow, J Horwitz; Sequencing, Tissue Specific Expression and Chaperone Activity of Zebrafish (Danio rerio) Alpha Crystallin . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4650.
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Purpose: To determine the nucleotide sequence, amino acid sequence and tissue specific expression of zebrafish αA-crystallin. To assess the chaperone activity of zebrafish αB-crystallin. Methods: 3' and 5' RACE was used to clone zebrafish αA-crystallin. The deduced peptide sequence was compared to various vertebrate orthologues using the algorithm CLUSTALW. αA-crystallin expression was evaluated in brain, heart, lens, liver, skeletal muscle/skin and spleen by semi-quantitative RT-PCR. The chaperone activity of recombinant zebrafish αB-crystallin was determined by measuring its ability to prevent the aggregation of denatured α-lactalbumin. Results: The 173 amino acid sequence of zebrafish αA-crystallin was determined to be 73% and 86% similar to its human and cavefish orthologues, respectively. High expression was detected in the lens and very low expression was detected in the spleen and liver. The chaperone activity of recombinant zebrafish αB-crystallin at 37° C was lower than that of recombinant human αB-crystallin. Approximately five times as much zebrafish αB-crystallin was needed to provide the same protection as the human orthologue. Conclusion: Few amino acids identified as being important to chaperone function differ between zebrafish and mammalian αA-crystallin. The expression of αA-crystallin is mainly confined to the lens in both taxa. Collectively, these data suggest that zebrafish αA-crystallin plays a physiologically limited role outside of the lens. Reduced chaperone function of zebrafish αB-crystallin at 37° C could indicate that this protein's protective role is less important in the zebrafish than in humans. Alternatively, this difference in chaperone activity could be due to thermal adaptation of the zebrafish protein to the lower body temperatures of this ectothermic species.
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