A fluorescent peptide model for the thioredoxin active site

Abstract

A synthetic model for the active site of the protein thioredoxin has been synthesized: Boc-Trp-Cys-Gly-Pro-Cys-NHMe corresponding to residues 31-35 of the protein and possessing the 14-membered disulfide loop and a fluorescent chromophore. Dithiothreitol reduction of the disulfide bond results in a 50-60% enhancement of Trp fluorescence. The rate of reduction is solvent dependent, following the order 8 M urea » methanol > water. The spectral changes observed in the model peptide are compared with those reported for the native protein. Circular dichroism studies suggest a substantial change in peptide backbone conformation, on disulfide reduction.