The novel transmembrane Escherichia coli proteins involved in the amino acid efflux

A novel gene of Escherichia coli, rhtB, has been characterized. Amplificati on of this gene provides resistance to homoserine and homoserine lactone. A nother E. coli gene, rhtC, provides resistance to threonine, The homologues of RhtB are widely distributed among various eubacteria and archaea, from one to 12 copies of family members that differ in their primary structure w ere found in the genomes. Most of them are genes that encode hypothetical t ransmembrane proteins. Experimental data that indicate participation of the rhtB product in the excretion of homoserine have been obtained. (C) 1999 F ederation of European Biochemical Societies.