The Escherichia coli PII signal transduction protein is activated upon binding 2-ketoglutarate and ATP.
Nitrogen regulation of transcription in Escherichia coli requires sensation of the intracellular nitrogen status and control of the dephosphorylation of the transcriptional activator NRI-P. This dephosphorylation is catalyzed by the bifunctional kinase/phosphatase NRII in the presence of the dissociable PII protein. The ability of PII to stimulate the phosphatase activity of NRII is regulated by a signal transducing uridylyltransferase/uridylyl-removing enzyme (UTase/UR), which converts PII to PII-UMP under conditions of nitrogen starvation; this modification prevents PII from stimulating the dephosphorylation of NRI approximately P. We used purified components to examine the binding of small molecules to PII, the effect of small molecules on the stimulation of the NRII phosphatase activity by PII, the retention of PII on immobilized NRII, and the regulation of the uridylylation of PII by the UTase/UR enzyme. Our results indicate that PII is activated upon binding ATP and either 2-ketoglutarate or glutamate, and that the liganded form of PII binds much better to immobilized NRII. We also demonstrate that the concentration of glutamine required to inhibit the uridylyltransferase activity is independent of the concentration of 2-ketoglutarate present. We hypothesize that nitrogen sensation in E. coli involves the separate measurement of glutamine by the UTase/UR protein and 2-ketoglutarate by the PII protein.
Kamberov
E S
ES
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606, USA.
Atkinson
M R
MR
Ninfa
A J
AJ
D000255:Adenosine Triphosphate / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism*; D018698:Glutamic Acid / Q000494:pharmacology; D005973:Glutamine / Q000494:pharmacology; D007656:Ketoglutaric Acids / Q000378:metabolism* / Q000494:pharmacology; D010071:Oxaloacetates / Q000494:pharmacology; D051922:PII Nitrogen Regulatory Proteins; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction
D001426:Bacterial Proteins; D007656:Ketoglutaric Acids; D010071:Oxaloacetates; D051922:PII Nitrogen Regulatory Proteins; D005973:Glutamine; D018698:Glutamic Acid; C404143:PIID regulatory protein, Bacteria; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C055699:protein kinase-phosphatase NTRB; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases