Time Resolved Fluorescence of the Single Tryptophan in R61, a DD-Carboxypeptidase from Streptomyces: Contributions of Dynamics and Heterogeneity

Abstract

The fluorescence emission of the single tryptophan (W233) of the mutant protein DD carboxypeptidase from streptomyces is characterized by a red edge excitation shift (REES). This phenomenon is an indication for strongly reduced dynamics in the environment of the tryptophan residue, which has a very low accessibility to the solvent. The Stokes shift however, shows an unusual temperature and time dependence. This, together with the fluorescence lifetime analysis, showing three resolvable lifetimes, can be explained by the presence of three rotameric states which can be identified using the Dead End Elimination (DEE) method.