Properties of the glucose-6-phosphate transporter from Chlamydia pneumoniae (HPTcp) and the glucose-6-phosphate sensor from Escherichia coli (UhpC).
The amino acid sequence of the proposed glucose-6-phosphate (Glc6P) transporter from Chlamydia pneumoniae (HPTcp; hexose phosphate transporter [Chlamydia pneumoniae]) exhibits a higher degree of similarity to the Escherichia coli Glc6P sensor (UhpC) than to the E. coli Glc6P transporter (UhpT). Overexpression of His-UhpC in a UhpT-deficient E. coli strain revealed that the sensor protein is also able to transport Glc6P and exhibits an apparent K(m) ((Glc6P)) of 25 microM, whereas His-HPTcp exhibits an apparent K(m)( (Glc6P)) of 98 microM. His-HPTcp showed a four-times-lower specific activity than His-UhpT but a 56-times-higher specific activity than His-UhpC. Like His-UhpT and His-UhpC, the carrier His-HPTcp performs a sugar-phosphate/inorganic-phosphate antiporter mode of transport. Surprisingly, while physiological concentrations of inorganic phosphate competitively inhibited transport mediated by the E. coli proteins His-UhpT and His-UhpC, transport mediated by His-HPTcp was not inhibited. Interestingly, C(3)-organophosphates stimulated His-HPTcp activity but not His-UhpT- or His-UhpC-catalyzed Glc6P transport. In contrast to His-UhpC, the His-HPTcp protein does not act as a Glc6P sensor in the uhp regulon.
Schwöppe
Christian
C
Pflanzenphysiologie, Universität Kaiserslautern, D-67653 Kaiserslautern, Germany.
Winkler
Herbert H
HH
Neuhaus
H Ekkehard
HE
D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D002352:Carrier Proteins / Q000737:chemistry / Q000502:physiology*; D016993:Chlamydophila pneumoniae / Q000737:chemistry*; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D019298:Glucose-6-Phosphate / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D026901:Membrane Transport Proteins; D010710:Phosphates / Q000494:pharmacology; D013379:Substrate Specificity
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010710:Phosphates; C490131:uhpC protein, E coli; C086587:uhpC protein, bacteria; D019298:Glucose-6-Phosphate