The EIIGlc protein is involved in glucose-mediated activation of Escherichia coli gapA and gapB-pgk transcription.
The Escherichia coli gapB gene codes for a protein that is very similar to bacterial glyceraldehyde-3-phosphate dehydrogenases (GAPDH). In most bacteria, the gene for GAPDH is located upstream of the pgk gene encoding 3-phosphoglycerate kinase (PGK). This is the case for gapB. However, this gene is poorly expressed and encodes a protein with an erythrose 4-phosphate dehydrogenase activity (E4PDH). The active GAPDH is encoded by the gapA gene. Since we found that the nucleotide region upstream of the gapB open reading frame is responsible for part of the PGK production, we analyzed gapB promoter activity in vivo by direct measurement of the mRNA levels by reverse transcription. We showed the presence of a unique transcription promoter, gapB P0, with a cyclic AMP (cAMP) receptor protein (CRP)-cAMP binding site centered 70.5 bp upstream of the start site. Interestingly, the gapB P0 promoter activity was strongly enhanced when glucose was used as the carbon source. In these conditions, deletion of the CRP-cAMP binding site had little effect on promoter gapB P0 activity. In contrast, abolition of CRP production or of cAMP biosynthesis (crp or cya mutant strains) strongly reduced promoter gapB P0 activity. This suggests that in the presence of glucose, the CRP-cAMP complex has an indirect effect on promoter gapB P0 activity. We also showed that glucose stimulation of gapB P0 promoter activity depends on the expression of enzyme IIGlc (EIIGlc), encoded by the ptsG gene, and that the gapA P1 promoter is also activated by glucose via the EIIGlc protein. A similar glucose-mediated activation, dependent on the EIIGlc protein, was described by others for the pts operon. Altogether, this shows that when glucose is present in the growth medium expression of the E. coli genes required for its uptake (pts) and its metabolism (gapA and gapB-pgk) are coordinately activated by a mechanism dependent upon the EIIGlc protein.
Charpentier
B
B
Maturation des ARN et Enzymologie Moléculaire, UMR CNRS 7567, Université H. Poincaré, Faculté des Sciences, 54506 Vandoeuvre-les-Nancy, Cedex, France.
Bardey
V
V
Robas
N
N
Branlant
C
C
D000445:Aldehyde Oxidoreductases / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D002244:Carbon; D000242:Cyclic AMP / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005947:Glucose / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics*; D008969:Molecular Sequence Data; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010735:Phosphoglycerate Kinase / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000378:metabolism; D015533:Transcriptional Activation
D002373:Cyclic AMP Receptor Protein; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D002244:Carbon; D000242:Cyclic AMP; D000445:Aldehyde Oxidoreductases; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; C066236:erythrose 4-phosphate dehydrogenase, E coli; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C031629:phosphoenolpyruvate-glucose phosphotransferase; D010735:Phosphoglycerate Kinase; D005947:Glucose