Overall control of nitrogen metabolism in Lactococcus lactis by CodY, and possible models for CodY regulation in Firmicutes.
CodY, a pleiotropic transcriptional regulator conserved in low G+C species of Gram-positive bacteria, was previously described to be the central regulator of proteolysis in Lactococcus lactis. In this study, over 100 potential CodY targets were identified by DNA-microarray analysis. Complementary transcriptional analysis experiments were carried out to validate the newly defined CodY regulon. Moreover, the direct role of CodY in the regulation of several target genes was demonstrated by gel retardation experiments. Interestingly, 45 % of CodY-dependent genes encode enzymes involved in amino acid biosynthesis pathways, while most of the other genes are involved in functions related to nitrogen supply. CodY of L. lactis represents the first example of a regulator in Gram-positive bacteria that globally controls amino acid biosynthesis. This global control leads to growth inhibition in several amino-acid-limited media containing an excess of isoleucine. A conserved 15 nt palindromic sequence (AATTTTCNGAAAATT), the so-called CodY-box, located in the vicinity of the -35 box of target promoter regions was identified. Relevance of the CodY-box as an operator for CodY was demonstrated by base substitutions in gel retardation experiments. This motif is also frequently found in the promoter region of genes potentially regulated by CodY in other Gram-positive bacteria.
Guédon
Eric
E
Génétique Microbienne, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas cedex, France.
Sperandio
Brice
B
Génétique Microbienne, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas cedex, France.
Pons
Nicolas
N
Génétique Microbienne, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas cedex, France.
Ehrlich
Stanislav Dusko
SD
Génétique Microbienne, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas cedex, France.
Renault
Pierre
P
Génétique Microbienne, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas cedex, France.
D001426:Bacterial Proteins; D004269:DNA, Bacterial / Q000032:analysis; D004268:DNA-Binding Proteins; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D013294:Lactococcus lactis / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D050436:Regulatory Elements, Transcriptional; D018085:Regulon; D012097:Repressor Proteins
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D009584:Nitrogen