Lysine represses transcription of the Escherichia coli dapB gene by preventing its activation by the ArgP activator.
The Escherichia coli dapB gene encodes one of the enzymes of the biosynthetic pathway leading to lysine and its immediate precursor, diaminopimelate. Expression of dapB is repressed by lysine, but no trans-acting regulator has been identified so far. Our analysis of the dapB regulatory region shows that sequences located in the -81/-118 interval upstream of the transcription start site are essential for full expression of dapB, as well as for lysine repression. Screening a genomic library for a gene that could alleviate lysine repression when present in multicopy led to the recovery of argP, a gene encoding an activating protein of the LysR-type family, known to use lysine as an effector. An argP null mutation strongly decreases dapB transcription that becomes insensitive to lysine. Purified His(6)-tagged ArgP protein binds with an apparent K(d) of 35 nM to the dapB promoter in a gel retardation assay, provided that sequences up to -103 are present. In the presence of L-lysine and L-arginine, the binding of ArgP to dapB is partly relieved. These results fit with a model in which ArgP contributes to enhanced transcription of dapB when lysine becomes limiting.
Bouvier
Jean
J
Université Paul Sabatier Toulouse III, Laboratoire de Microbiologie et Génétique Moléculaire, F31000 Toulouse, France.
Stragier
Patrick
P
Morales
Violette
V
Rémy
Elisabeth
E
Gutierrez
Claude
C
D001120:Arginine / Q000378:metabolism; D019677:Artificial Gene Fusion; D001483:Base Sequence; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D050746:Dihydrodipicolinate Reductase / Q000096:biosynthesis*; D024202:Electrophoretic Mobility Shift Assay; D004926:Escherichia coli / Q000201:enzymology / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008239:Lysine / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C068863:argP protein, E coli; D001120:Arginine; D050746:Dihydrodipicolinate Reductase; D001616:beta-Galactosidase; D008239:Lysine