Family

Phosphotransferase system, lactose/cellobiose-type IIA subunit (IPR003188)

Short name: PTS_IIA_lac/cel

Family relationships

None.

Description

The phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS) [PMID: 8246840, PMID: 2197982] 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 [PMID: 1537788]. 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 [PMID: 8246840, PMID: 1537788, PMID: 7815935, PMID: 11361063].

The lactose/cellobiose-specific family are one of four structurally and functionally distinct group IIA PTS system enzymes. This family of proteins normally function as a homotrimer, stabilised by a centrally located metal ion [PMID: 9261069]. Separation into subunits is thought to occur after phosphorylation.

GO terms

Biological Process

GO:0009401 phosphoenolpyruvate-dependent sugar phosphotransferase system

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
CDD
PANTHER
PIRSF
Pfam
PROSITE profiles
TIGRFAMs