The Klebsiella pneumoniae PII protein (glnB gene product) is not absolutely required for nitrogen regulation and is not involved in NifL-mediated nif gene regulation

Abstract

The role of the Klebsiella pneumoniae PII protein (encoded by glnB) in nitrogen regulation has been studied using two classes of glnB mutants. In Class I mutants PII appears not to be uridylylated in nitrogen-limiting conditions and in Class II mutants PII is not synthesised. The effects of these mutations on expression from nitrogen-regulated promoters indicate that PII is not absolutely required for nitrogen control. Furthermore the uridylylated form of PII (PII-UMP) plays a significant role in the response to changes in nitrogen status by counteracting the effect of PII on NtrB-mediated dephosphorylation of NtrC. PII is not involved in the nif-specific response to changes in nitrogen status mediated by NifL.