Energy transfer distance distributions recovered from a zinc finger peptide using time-resolved frequency-domain fluorometry

摘要

The "zinc finger" motif, found in nucleic acid-binding proteins, consists of a peptide domain which tetrahedrally coordinates a zinc ion via cysteine (sulfhydryl) and histidine (imadazole nitrogen) sidechain atoms. The CCHH class, in which zinc binds to a pair of cysteines and a pair of histidines, is commonly found in eukaryotic transcription factors. These transcription factors cannot bind DNA in the absence of metal ion, and physical studies (CD, NMR) indicate that a more defined structure is induced upon metal binding. Fluorescence energy transfer measurements were performed on a zinc finger peptide which contains a single CCHH metal-binding domain. An intrinsic conserved tryptophan, located at the midpoint of the peptide chain, serves as the energy donor to one of two dansyl acceptors (one acceptor is attached to the α-amino group and the other to the ε-amino group of a carboxy-terminal lysine). Distance distributions between the donor and acceptor were determined for zinc-bound and metal-free peptide using time-resolved frequency-domain fluorometry. The distance distributions were shorter and narrower for the zinc-bound peptide than those recovered for the zinc-free peptide. These results confirm previous experimental evidence which indicates that metal ion is required to form a well-defined solution conformation.