There are two tryptophan residues in the lens αB-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 β-strand.