Evidence for an Arginine Exporter Encoded by yggA ( argO ) That Is Regulated by the LysR-Type Transcriptional Regulator ArgP in Escherichia coli

Abstract

The anonymous open reading frame yggA of Escherichia coli was identified in this study as a gene that is under the transcriptional control of argP (previously called iciA), which encodes a LysR-type transcriptional regulator protein. Strains with null mutations in either yggA or argP were supersensitive to the arginine analog canavanine, and yggA-lac expression in vivo exhibited argP ؉ -dependent induction by arginine. Lysine supplementation phenocopied the argP null mutation in that it virtually abolished yggA expression, even in the argP ؉ strain. The dipeptides arginylalanine and lysylalanine behaved much like arginine and lysine, respectively, to induce and to turn off yggA transcription. Dominant missense mutations in argP (argP d ) that conferred canavanine resistance and rendered yggA-lac expression constitutive were obtained. The protein deduced to be encoded by yggA shares similarity with a basic amino acid exporter (LysE) of Corynebacterium glutamicum, and we obtained evidence for increased arginine efflux from E. coli strains with either the argP d mutation or multicopy yggA ؉ . The null yggA mutation abolished the increased arginine efflux from the argP d strain. Our results suggest that yggA encodes an ArgP-regulated arginine exporter, and we have accordingly renamed it argO (for "arginine outward transport"). We propose that the physiological function of argO may be either to prevent the accumulation to toxic levels of canavanine (which is a plant-derived antimetabolite) or arginine or to maintain an appropriate balance between the intracellular lysine and arginine concentrations.

Distinct Paths for Basic Amino Acid Export in Escherichia coli: YbjE (LysO) Mediates Export of l -Lysine

“…If required, the kanamycin resistance determinant marking the null mutation sourced from the Keio collection was excised by treatment with the plasmid pCP20 as described earlier (22). The molecular characterization of the argO::205Tn10dTet insertion in argO that abolishes ArgO function has been described previously (5). The plasmids used in this study are derivatives of the plasmids pACYC184 (23), pTrc99A (24), pCL1920 (25), and pMU575 (26), and their construction is described in Table 1.…”

“…In C. glutamicum, LysE mediates export of the basic amino acids L-arginine (Arg) and L-lysine (Lys) (15,16), whereas its ortholog in E. coli ArgO so far has been thought to promote export only of Arg (5), and evidence for ArgO-mediated Lys export is as yet unavailable. In the present study, we ascribe a Lys export function to the product of ybjE, present on the E. coli chromosome.…”

“…For example, Escherichia coli encodes multiple proteins for the export of sugars, such as glucose and lactose (1), and for arabinose (2,3). In addition, the occurrence of proteins mediating export of amino acids, such as alanine (4), arginine (5), aromatic amino acids (6), cysteine (7,8), leucine (9), threonine (10,11) and valine (12), in E. coli has been reported. While the physiological basis for the existence of amino acid exporters is not clear, their occurrence is relatively widespread in bacteria (13,14).…”

“…An alternative view could be that export of the amino acid occurs by chance, with the cognate substrate being a naturally occurring structurally related antimetabolite present in the environment. As an example of the latter, one mechanism contributing to the resistance of E. coli to the plant-derived antimetabolite canavanine (CAN), an L-arginine analogue, involves its export by ArgO, the ortholog of the basic amino acid exporter LysE of Corynebacterium glutamicum, following its uptake (5). Harnessing the amino acid export potential of a given bacterium has found widespread application in the commercial production of amino acids (reviewed in references 13 and 14).…”

Molecular characterization of lysR-lysXE, gcdR-gcdHG and amaR-amaAB operons for lysine export and catabolism: a comprehensive lysine catabolic network in Pseudomonas aeruginosa PAO1

“…The lysX gene codes for a protein of unknown function while the lysE gene codes for a putative amino acid exporter of the LysE/ArgO family, showing 45 % sequence identity to the arginine exporter ArgO and the lysine exporter LysO of E. coli (Nandineni & Gowrishankar, 2004;Pathania & Sardesai, 2015). Upstream of the lysXE operon, the divergent lysR gene was annotated as iciA (Thöny et al, 1991) by the genome project, and the transcriptional regulator encoded exhibited 41 % sequence identity to ArgP of E. coli in control of ArgO expression.…”