Control of the expression of the manXYZ operon in Escherichia coli: Mlc is a negative regulator of the mannose PTS.
The manXYZ operon of Escherichia coli encodes a sugar transporter of the phosphoenol pyruvate (PEP)-dependent phosphotransferase system, which is capable of transporting many sugars, including glucose, mannose and the aminosugars, glucosamine and N-acetylglucosamine. Transcription of manX is strongly dependent on cyclic AMP (cAMP)/cAMP receptor protein (CAP). A cAMP/CAP binding site is located at -40.5, and activation by cAMP/CAP is shown to be typical of a class II promoter. The 5' end of a transcript, potentially encoding two proteins, is expressed divergently from the manXYZ operon. Previously, two binding sites for the NagC repressor were detected upstream of manX, but a mutation in nagC has very little effect on manX expression. However, a mutation in the mlc gene, encoding a homologue of nagC, results in a threefold derepression of manX expression, suggesting that this protein is a more important regulator of manX expression than NagC. The Mlc protein binds to the NagC operators, binding preferentially to the promoter-proximal operator. Plasmids overproducing either the NagC protein or the Mlc protein repress the expression of manX, but the effect of the Mlc protein is stronger. The mlc gene is shown to be allelic with the previously characterized dgsA mutation affecting the mannose phosphoenolpyruvate-dependent phosphotransferase system (PTS).
Plumbridge
J
J
Institut de Biologie Physico-chimique (UPR9073), Paris, France. plumbridge@ibpc.fr
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D000242:Cyclic AMP; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009876:Operon; D010442:Peptide Chain Initiation, Translational; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C111065:Mlc protein, E coli; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; C065503:bor protein, Bacteriophage lambda; C067862:nagC protein, E coli; D000242:Cyclic AMP; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C037992:phosphoenolpyruvate-mannose phosphotransferase