Expression of the pho regulon interferes with induction of the uhpT gene in Escherichia coli K-12.
The uptake of hexose 6-phosphates in Escherichia coli is mediated by the transporter UhpT, the synthesis of which is induced by the presence of glucose 6-phosphate (glucose 6-P) in the medium. Since this protein functions as an anion exchanger, it is generally assumed to be geared for the use of sugar phosphates as a carbon source. However, the question was unresolved whether this transporter can also provide the cells with glucose 6-P as a phosphate source. It is demonstrated in this work that UhpT-mediated glucose 6-P uptake does not allow the cells to grow on glucose 6-P as phosphate source. Hence, the expression of UhpT under phosphate limitation would not be particularly advantageous and some form of interaction between the uhp system and the Pi-limitation-inducible pho regulon, the products of which are involved in phosphate acquisition, may be anticipated. Indeed, the use of an uhpT-lacZ fusion revealed that much higher concentrations of the inducer glucose 6-P were required to elevate uhpT transcription when the pho regulon was expressed. This interference was the result of degradation of glucose 6-P by one of the products of the pho regulon, the periplasmic enzyme alkaline phosphatase. The specific form of interaction between the Pho and Uhp systems is designated inducer degradation.
Hoffer
S M
SM
Department of Molecular Microbiology, Utrecht University, 3584 CH Utrecht, The Netherlands.
van Uden
N
N
Tommassen
J
J
D000469:Alkaline Phosphatase / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D019298:Glucose-6-Phosphate / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010710:Phosphates / Q000378:metabolism*; D018085:Regulon / Q000502:physiology*
D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D010710:Phosphates; C063498:UhpT protein, E coli; D019298:Glucose-6-Phosphate; D000469:Alkaline Phosphatase