The Journal of Bacteriology, 2000, Vol. 182(16), p.4443
In Escherichia coli K-12, the major glucose transporter with a central role in carbon catabolite repression and in inducer exclusion is the phosphoenolpyruvate-dependent glucose:phosphotransferase system (PTS). Its membrane-bound subunit, IICB super(Glc), is encoded by the gene ptsG; its soluble domain, IIA super(Glc), is encoded by crr, which is a member of the pts operon. The system is inducible by D-glucose and, to a lesser degree, by L-sorbose. The regulation of ptsG transcription was analyzed by testing the induction of IICB super(Glc) transporter activity and of a single-copy Phi (ptsGop-lacZ) fusion. Among mutations found to affect directly ptsG expression were those altering the activity of adenylate cyclase (cyaA), the repressor DgsA (dgsA; also called Mlc), the general PTS proteins enzyme I (ptsI) and histidine carrier protein HPr (ptsH), and the IIA super(Glc) and IIB super(Glc) domains, as well as several authentic and newly isolated UmgC mutations. The latter, originally thought to map in the repressor gene umgC outside the ptsG locus, were found to represent ptsG alleles. These affected invariably the substrate specificity of the IICB super(Glc) domain, thus allowing efficient transport and phosphorylation of substrates normally transported very poorly or not at all by this PTS. Simultaneously, all of these substrates became inducers for ptsG. From the analysis of the mutants, from cis-trans dominance tests, and from the identification of the amino acid residues mutated in the UmgC mutants, a new regulatory mechanism involved in ptsG induction is postulated. According to this model, the phosphorylation state of IIB super(Glc) modulates IIC super(Glc) which, directly or indirectly, controls the repressor DgsA and hence ptsG expression. By the same mechanism, glucose uptake and phosphorylation also control the expression of the pts operon and probably of all operons controlled by the repressor DgsA.
Escherichia Coli ; Escherichia Coli ; Carbon ; Gene Fusion ; Operons ; Catabolite Repression ; Gene Regulation ; Carbon ; Gene Fusion ; Operons ; Catabolite Repression ; Gene Regulation ; Lacz Gene ; Ptsg Gene ; Dgsa Protein ; Glucose Transporters ; Lacz Gene ; Ptsg Gene ; Dgsa Protein ; Glucose Transport ; Mutagenesis Techniques ; Enzymes ; Dgsa Protein ; Glucose Transport ; Glucose Transporters ; Lacz Gene ; Ptsg Gene;
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