CRYSTAL-STRUCTURE OF THE DIPEPTIDE BINDING-PROTEIN FROM ESCHERICHIA-COLI INVOLVED IN ACTIVE-TRANSPORT AND CHEMOTAXIS

The Escherichia coli periplasmic dipeptide binding protein functions i n both peptide transport and taxis toward peptides. The structure of t he dipeptide binding protein in complex with Gly-Leu (glycyl-L-leucine ) has been determined at 3.2 Angstrom resolution. The binding site for dipeptides is designed to recognize the ligand's backbone while provi ding space to accommodate a variety of side chains. Some repositioning of protein side chains lining the binding site must occur when the di peptide's second residue is larger than leucine. The protein's fold is very similar to that of the Salmonella typhimurium oligopeptide bindi ng protein, and a comparison of the structures reveals the structural basis for the dipeptide binding protein's preference for shorter pepti des.