The Trg transducer of E. coli, located in cytoplasmic membrane mediates attractant response to ribose. The periplasmic ribose-binding protein (RBP) is encoded by rbsB gene and is thought to interact with Trg transducer. Ligand-occupied ribose-binding protein is supposed to exert chemotatic response by binding to the Trg transducer and to transport ribose into the cytoplasm. To study the interaction of RBP with Trg, we used trg-8 mutation (Arg85His) that has specific defects in chemotactic response to ribose. We have mutagenized pA112 plasmid containing rbsB gene with hydroxylamine. The mutagenized rbsB plasmids were introduced into the strain that has trg-8 mutation and then ribose taxis positive transformants were screened on ribose swarm plate. Four suppressors that restore ribose taxis have been isolated. Two of the mutations were sequenced by DNA sequencing to find their mutational changes. One has Glu191Lys change and the other Pro65Ser. These results suggest that the residues of 65 and 191 of RBP are important for the interaction with Trg transducer. The structural role and significance of these residues in receptor interaction are discussed based on their locations in three dimensional structure of RBP generated by computer modelling.