A model of photoprobe docking with β1,4-galactosyltransferase identifies a possible carboxylate involved in glycosylation steps

galactosyltransferase with an acceptor site photoprobe. This is based on an acceptor site peptide fragment which was recently identified by the use of a photoprobe. The present model strongly suggests that the carboxylate group of Asp318 could be involved in the activation of the acceptor sugar 4-OH for the efficient galactosyltransfer. The result also exemplified that the combination of photoaffinity labeling with crystallography is a powerful method for the detailed structural analysis of ligand–protein complex.