title: Two periplasmic transport proteins which interact with a common membrane receptor show extensive homology: complete nucleotide sequences.
abstract: The hisJ and argT genes of Salmonella typhimurium encode two periplasmic binding proteins, J and LAO, which are involved in histidine and arginine transport, respectively, and which interact with a common membrane-bound component, the P protein. The complete nucleotide sequences of these two genes have been determined. The two genes show extensive homology (70%) and presumably arose by tandem duplication of a single ancestral gene. The two encoded proteins now perform distinct functions but still retain sufficient homology to permit interaction with the same site on the membrane-bound P protein. Three lines of evidence have allowed both the amino acid-binding site and the site involved in the interaction with the P protein to be assigned to specific regions of each binding protein: (i) the distribution of amino acid differences between the two proteins; (ii) the properties of a functional chimeric protein, produced by a deletion mutant in which the first half of the argT gene is fused to the second half of the hisJ gene; (iii) the sequence change in a mutant J protein unable to interact with P.
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics*; D002462:Cell Membrane / Q000378:metabolism; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000235:genetics; D005796:Genes; D006639:Histidine / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation; D011955:Receptors, Drug / Q000235:genetics*; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins; D011955:Receptors, Drug; D006639:Histidine; D001120:Arginine; D004262:DNA Restriction Enzymes