MAPPING, CLONING, EXPRESSION, AND SEQUENCING OF THE RHAT GENE, WHICH ENCODES A NOVEL L-RHAMNOSE-H-TYPHIMURIUM AND ESCHERICHIA-COLI( TRANSPORT PROTEIN IN SALMONELLA)

A L-rhamnose transport-negative strain of Escherichia coli was generat ed by Mu d(Ap(R),lac)I mutagenesis. This strain was used to isolate a clone of Salmonella typhimurium DNA that encoded L-rhamnose-H+ transpo rt activity, the gene for which, rhaT, was sequenced. The rhaT gene wa s mapped on the E. coli chromosome between rhaR and sodA at 87.9 min, initially by Southern blot analysis and then by the isolation, express ion, and sequencing of the rhaT gene. Both rhaT genes encoded a hydrop hobic protein of 344 amino acids (91% identical) that contained 10 put ative transmembrane regions. The RhaT protein represents a novel class of sugar transport protein.