Control of the Bacillus subtilis Antiterminator Protein GlcT by Phosphorylation

Abstract

transports glucose by the phosphotransferase system (PTS). The genes for this system are encoded in the operon, which is induced by glucose and depends on a termination/antitermination mechanism involving a riboswitch and the RNA-binding antitermination protein GlcT. In the absence of glucose, GlcT is inactive, and a terminator is formed in the leader region of the mRNA. If glucose is present, GlcT can bind to its RNA target and prevent transcription termination. The GlcT protein is composed of three domains, an N-terminal RNA binding domain and two PTS regulation domains, PTS regulation domain (PRD) I and PRD-II. In this work, we demonstrate that GlcT can be phosphorylated by two PTS proteins, HPr and the glucose-specific enzyme II (EII). HPr-dependent phosphorylation occurs on PRD-II and has a slight stimulatory effect on GlcT activity. In contrast, EII phosphorylates the PRD-I of GlcT, and this phosphorylation inactivates GlcT. This latter phosphorylation event links the availability of glucose to the expression of the operon via the phosphorylation state of EII and GlcT. This is the first demonstration of a direct phosphorylation of an antiterminator of the BglG family by the corresponding PTS permease