Expression control and specificity of the basic amino acid exporter LysE of Corynebacterium glutamicum.
LysE of Corynebacterium glutamicum belongs to a large new superfamily of translocators whose members are probably all involved in the export of small solutes. Here, the transcript initiation site of lysE, and its divergently transcribed regulator gene, lysG, are identified. Single-copy transcriptional fusions of lysE with lacZ, and titration experiments, show that LysG is the positive regulator of lysE expression enabling its up to 20-fold induction. This induction requires the presence of a coinducer, which is either intracellular L-lysine, or L-arginine. A competition experiment showed that LysE exports these two basic amino acids at comparable rates of about 0.75 nmol min(-1) (mg dry wt)(-1). Although L-histidine and L-citrulline also act as coinducers of lysE expression, these two amino acids are not exported by LysE. As is evident from the analysis of a lysEG deletion mutant, the physiological role of the lysEG system is to prevent bacteriostasis due to elevated L-lysine or L-arginine concentrations that arise during growth in the presence of peptides or in mutants possessing a deregulated biosynthesis pathway. C. glutamicum has additional export activities other than those of LysE for exporting L-histidine, L-citrulline and L-ornithine.
Bellmann
A
A
Institut für Biotechnologie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany1.
Vrljić
M
M
Institut für Biotechnologie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany1.
Pátek
M
M
Institute of Microbiology, Academy of Sciences, CZ-14220 Prague, Czech Republic2.
Sahm
H
H
Institut für Biotechnologie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany1.
Krämer
R
R
Institut für Biochemie, Universität zu Köln, Zülpicher Strasse 47, D-57674 Köln, Germany3.
Eggeling
L
L
Institut für Biotechnologie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany1.
D026923:Amino Acid Transport Systems, Basic; D000599:Amino Acids, Diamino / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003352:Corynebacterium / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D013379:Substrate Specificity; D014158:Transcription, Genetic
D026923:Amino Acid Transport Systems, Basic; D000599:Amino Acids, Diamino; D001426:Bacterial Proteins; D002352:Carrier Proteins; C104616:LysE protein, Corynebacterium glutamicum; C438905:LysG protein, Corynebacterium glutamicum