Mutational analysis of ligand recognition by Tcp, the citrate chemoreceptor of Salmonella enterica serovar typhimurium

The chemoreceptor Tcp mediates taxis to citrate. To identify citrate-bindin g residues, we substituted cysteine for seven basic or polar residues that are chosen based on the comparison of Tcp with the well-characterized chemo receptors. The results suggest that Arg-63, Arg-68, Arg-72, Lys-75, and Tyr -150 (and probably other unidentified residues) are involved in the recogni tion of citrate.