PTS_IIB_bgl_like: the PTS (phosphotransferase system) IIB domain of a family of sensory systems composed of a membrane-bound sugar-sensor (similar to BglF) and a transcription antiterminator (similar to BglG) which regulate expression of genes involved in sugar utilization. The domain architecture of the IIB-containing protein includes a region N-terminal to the IIB domain which is homologous to the BglG transcription antiterminator with an RNA-binding domain followed by two homologous domains, PRD1 and PRD2 (PTS Regulation Domains). C-terminal to the IIB domain is a domain similar to the PTS IIA domain. In this system, the BglG-like region and the IIB and IIA-like domains are all expressed together as a single multidomain protein. The IIB domain fold includes a central four-stranded parallel open twisted beta-sheet flanked by alpha-helices on both sides. The seven major PTS systems with this IIB fold include this sensory system with similarity to the bacterial bgl system, chitobiose/lichenan, ascorbate, lactose, galactitol, mannitol, and fructose systems.
Comment:most of the active site residues are contained within a P-loop which forms part of a binding pocket for the phosphoryl group
Comment:for the E coli chitobiose transporter IIB subunit, in addition to the P-loop residues, two conserved residues are likely to be important in catalysis: a tyrosine whose side-chain points towards the phosphorylation site and a Gln residue whose side-chain lies close to the sulfur atom of the catalytic cysteine.