A 3RD PERIPLASMIC TRANSPORT-SYSTEM FOR L-ARGININE IN ESCHERICHIA-COLI - MOLECULAR CHARACTERIZATION OF THE ARTPIQMJ GENES, ARGININE BINDING AND TRANSPORT

A new binding-protein-dependent transport system of Escherichia coli specific for L-arginine was characterized by genetic and biochemical means. The system is encoded by five adjacent genes, artPIQMJ(art standing for arginine transport), which are organized in two transcriptional units (artPIQM and artJ). The artI and artJ gene products (ArtI and ArtJ) are periplasmic binding proteins with sequence similarity to binding proteins for polar (basic) amino acids. The artQ, artM and artP products are similar to the transmembraneous proteins and the ATPase of binding-protein-dependent carriers. The mature ArtI and J proteins were localized in the periplasm and lacked signal peptides of 19 amino acid residues. ArtI and ArtJ were isolated from overproducing strains. ArtJ specifically binds L-arginine with high affinity and overproduction of ArtJ stimulated L-arginine uptake by the bacteria. The substrate for ArtI is not known, and isolated ArtI did not bind common amino acids, various basic uncommon amino acids or amines. It is concluded that the artPIQM artJ genes encode a third arginine-uptake system in addition to the known argT hisJQMP system of Salmonella typhimurium and E. coli and the arginine (-ornithine) carrier (aps) of E. coli.