| Primary Identifier | IPR036542 | Type | Homologous_superfamily |
| Short Name | PTS_IIA_lac/cel_sf |
| description | The phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS) [, ]is a major carbohydrate transport system in bacteria. The PTS catalyses the phosphorylation of incoming sugar substrates and coupled with translocation across the cell membrane, makes the PTS a link between the uptake and metabolism of sugars.The general mechanism of the PTS is the following: a phosphoryl group from phosphoenolpyruvate (PEP) is transferred via a signal transduction pathway, to enzyme I (EI) which in turn transfers it to a phosphoryl carrier, the histidine protein (HPr). Phospho-HPr then transfers the phosphoryl group to a sugar-specific permease, a membrane-bound complex known as enzyme 2 (EII), which transports the sugar to the cell. EII consists of at least three structurally distinct domains IIA, IIB and IIC []. These can either be fused together in a single polypeptide chain or exist as two or three interactive chains, formerly called enzymes II (EII) and III (EIII). The first domain (IIA or EIIA) carries the first permease-specific phosphorylation site, a histidine which is phosphorylated by phospho-HPr. The second domain (IIB or EIIB) is phosphorylated by phospho-IIA on a cysteinyl or histidyl residue, depending on the sugar transported. Finally, the phosphoryl group is transferred from the IIB domain to the sugar substrate concomitantly with the sugar uptake processed by the IIC domain. This third domain (IIC or EIIC) forms the translocation channel and the specific substrate-binding site. An additional transmembrane domain IID, homologous to IIC, can be found in some PTSs, e.g. for mannose [, , , ]. The lactose/cellobiose-specific superfamily are one of four structurally and functionally distinct group IIA PTS system enzymes. This superfamily of proteins normally function as a homotrimer, stabilised bya centrally located metal ion []. Separation into subunits is thought to occur after phosphorylation. It has a spectrin repeat-like fold which consists of three helices arranged in a close bundle with left-handed twist going up-and-down. |
