The phosphotransferase protein EIIANtr modulates the phosphate starvation response through interaction with histidine kinase PhoR in Escherichia coli

Abstract

Many Proteobacteria possess the paralogous PTSNtr, in addition to the sugar transport phosphotransferase system (PTS). In the PTSNtr phosphoryl-groups are transferred from phosphoenolpyruvate to protein EIIANtr via the phosphotransferases EINtr and NPr. The PTSNtr has been implicated in regulation of diverse physiological processes. In Escherichia coli, the PTSNtr plays a role in potassium homeostasis. In particular, EIIANtr binds to and stimulates activity of a two-component histidine kinase (KdpD) resulting in increased expression of the genes encoding the high-affinity K+ transporter KdpFABC. Here, we show that the phosphate (pho) regulon is likewise modulated by PTSNtr. The pho regulon, which comprises more than 30 genes, is activated by the two-component system PhoR/PhoB under conditions of phosphate starvation. Mutants lacking EIIANtr are unable to fully activate the pho genes and exhibit a growth delay upon adaptation to phosphate limitation. In contrast, pho expression is increased above the wild-type level in mutants deficient for EIIANtr phosphorylation suggesting that non-phosphorylated EIIANtr modulates pho. Protein interaction analyses reveal binding of EIIANtr to histidine kinase PhoR. This interaction increases the amount of phosphorylated response regulator PhoB. Thus, EIIANtr is an accessory protein that modulates the activities of two distinct sensor kinases, KdpD and PhoR, in E.coli. © 2012 Blackwell Publishing Ltd.