DETERMINATION OF THE BINDING FRAME OF THE CHAPERONE SECB WITHIN THE PHYSIOLOGICAL LIGAND OLIGOPEPTIDE-BINDING PROTEIN

Chaperone proteins demonstrate the paradoxical ability to bind ligands rapidly and with high affinity but with no apparent sequence specific ity. To learn more about this singular property, we have mapped the bi nding frame of the chaperone SecB from E. coli on the oligopeptide-bin ding protein. Similar studies performed on the maltose-binding and gal actose-binding proteins revealed centrally positioned binding frames o f similar to 160 aminoacyl residues. The work described here shows tha t OppA, which is significantly longer than the previously studied liga nds, has a binding frame that covers 460 amino acids, nearly the entir e length of the protein. We propose modes of binding to account for th e data.