Seven ribose-binding protein(RBP) mutations defective in chemotaxis were characterized by equilibrium-binding and ribose uptake assay. The rbsB301 mutant protein shows no uptake and reduced affinity to ribose. However, the others have similar affinity to ribose as wild type. They exibit variable degree of chemotatic response to ribose mediated by Trg chemosensory receptor.
A screening system to isolate RBP mutations specically defective in chemotaxis was developed by using a chimeric transducer, termed Trz, made between Trg receptor and EnvZ osmosensor. The feasibility of this system to be used for mutant screening was investigated.
It seems possible that the use of DTNB in screenig let us select some silent changes of cysteine residues around functionally critical region of RBP.
