AUTOPHOSPHORYLATION AND ACTIVATION OF TRANSCRIPTIONAL ACTIVATOR PHOB OF ESCHERICHIA-COLI BY ACETYL PHOSPHATE IN-VITRO

The PhoB protein, the transcriptional activator for the genes belongin g to the phosphate regulon in Escherichia coli, was autophosphorylated in the presence of acetyl phosphate (acP) in vitro. The properties of phospho-PhoB, such as stability upon acid or alkali treatment and act ivating pstS transcription by RNA polymerase holoenzyme, were the same as those of phospho-PhoB produced from phospho-PhoR or phospho-PhoM. These results indicate that PhoB is an enzyme that catalyzes its own p hosphorylation using acP, a low-molecular-weight metabolic intermediat e.