title: Phosphorylation site of NtrC, a protein phosphatase whose covalent intermediate activates transcription.
abstract: The NtrC transcription factor is a member of a family of homologous prokaryotic regulatory proteins that participate in the transduction of extracellular and nutritional signals. It has been demonstrated that the phosphate group from a histidine residue of the phosphorylated NtrB protein autokinase is transferred to the NtrC protein. Phosphorylation of the NtrC protein is transient and activates its transcriptional enhancement activity. We have investigated the site of phosphorylation of the Salmonella typhimurium NtrC protein and find that it is an aspartate residue (Asp-54) that is found within a sequence conserved in all of the members of the family of regulatory proteins. We propose that this phosphorylation is an NtrC protein histidine phosphatase catalytic intermediate. This conclusion suggests that the NtrC family should be viewed not as kinase substrates but as enzymes that can catalyze the hydrolysis of their activated forms in a concentration-independent fashion. They are similar in this sense to eukaryotic signal-transducing GTPases.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: D A
authors.initials: DA
authors.lastname: Sanders
authors.forename: B L
authors.initials: BL
authors.lastname: Gillece-Castro
authors.forename: A L
authors.initials: AL
authors.lastname: Burlingame
authors.forename: D E
authors.initials: DE
authors.lastname: Koshland
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D020558:GTP Phosphohydrolases / Q000032:analysis; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000502:physiology; D010766:Phosphorylation; D014157:Transcription Factors / Q000737:chemistry*
chemical_list: D014157:Transcription Factors; D010749:Phosphoprotein Phosphatases; D000251:Adenosine Triphosphatases; D020558:GTP Phosphohydrolases