Spectral contribution of the individual tryptophan of alphaB-crystallin: a study by site-directed mutagenesis.
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.
Liang
J J
JJ
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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T X
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Akhtar
N J
NJ
D019943:Amino Acid Substitution; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry*
D003459:Crystallins; D014364:Tryptophan