Mediates the positive regulation of the glucose PTS operon (ptsGHI) by functioning as an antiterminator factor of transcription via its interaction with the RNA-antiterminator (RAT) sequence located upstream of the ptsG gene. The RNA-binding domain of GlcT directly binds to the RNA antiterminator (RAT) sequence and prevents transcriptional termination. GlcT binding requires two identical and nearly symmetrical triple base pairings in the RAT sequence. Homodimer (By similarity). The monomeric form probably also exists but it would be inactive in RNA binding and antitermination. Composed of 3 domains: an N-terminal RNA-binding domain that prevents transcriptional termination, and two PTS regulation domains, PRD 1 and PRD 2. PRD 1 is the target of negative control exerted by EII-Glc and PRD 2 is the target of HPr. Phosphorylated by HPr (PtsH) and EII-Glc (PtsG). HPr phosphorylates the PRD 2 domain which has a slight stimulatory effect on GlcT activity, while EII-Glc phosphorylates the PRD 1 domain which inactivates GlcT. The phosphorylation is dependent on the presence or absence of glucose which acts as an inducer of the ptsGHI operon expression. In the presence of glucose the phosphoryl group is transferred from phosphorylated HPr to the sugar via EII-Glc. Under these conditions GlcT is not phosphorylated and binds to the RAT sequence, thus allowing transcription of the ptsGHI operon. In the absence of glucose, phosphorylated EII-Glc accumulates in the cell and phosphorylates the PRD 1 domain of GlcT, leading to its inactivation; this phosphorylation may prevent dimerization of GlcT. Belongs to the transcriptional antiterminator BglG family. GlcT subfamily.