Spectral contribution of the individual tryptophan of alphaB-crystallin: a study by site-directed mutagenesis |
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Authors: | Liang J J Sun T X Akhtar N J |
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Institution: | Center for Ophthalmic Research, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. jliang@rics.bwh.harvard.edu |
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Abstract: | There are two tryptophan residues in the lens alphaB-crystallin, Trp9 and Trp60. We prepared two Trp --> Phe substituted mutants, W9F and W60F, for use in a spectroscopic study. The two tryptophan residues contribute to Trp fluorescence and near-ultraviolet circular dichroism (UV CD) differently. The major difference in the near-UV CD is the contribution of 1La of Trp: it is positive in W60F but becomes negative in W9F. Further analysis of the near-UV CD shows an increased intensity in the region of 270-280 nm for W60F, suggesting that the Tyr48 is affected by the W60F mutation. It appears that Trp60 is located in a more rigid environment than Trp9, which agrees with a recent structural model in which Trp60 is in a beta-strand. |
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Keywords: | αA-crystallin αB-crystallin circular dichroism fluorescence Tip → Phe mutant |
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