INVOLVEMENT OF PHOSPHOTRANSACETYLASE, ACETATE KINASE, AND ACETYL PHOSPHATE SYNTHESIS IN CONTROL OF THE PHOSPHATE REGULON IN ESCHERICHIA-COLI

Two controls of the phosphate (PHO) regulon require sensor proteins that are protein kinases that phosphorylate the regulator, PhoB, which in turn activates transcription only when phosphorylated. P(i) control requires the P(i) sensor PhoR; the other control is P(i) independent and requires the sensor CreC (formerly called PhoM). Here we describe an additional control of the PHO regulon which is P(i) independent and requires neither PhoR nor CreC. This control is regulated by a two-step pathway in carbon metabolism in which acetyl coenzyme A, P(i), and ADP are converted into acetate, coenzyme A, and ATP via the enzymes phosphotransacetylase (Pta) and acetate kinase (AckA). It responds to the synthesis of acetyl phosphate, an intermediate in the Pta-AckA pathway. Since the synthesis of acetyl phosphate via this pathway leads to the incorporation of P(i) into ATP, the primary phosphoryl donor in metabolism, we propose that a regulatory coupling(s) may exist between the PHO regulon, which encodes genes for P(i) uptake, and genes for enzymes in central metabolism for incorporation of P(i) into ATP. Regulatory interactions of this sort may be important in global control. Further, it provides a functional basis for the concept of cross-regulation in the PHO regulon. This is also the first evidence that acetyl phosphate may have a role as an effector of gene regulation.