Phosphotransferase system EIIB component, mannitol-specific (IPR029503)

Short name: PTS_EIIB_mannitol

Overlapping homologous superfamilies

Domain relationships


The bacterial phosphoenolpyruvate: sugar phosphotransferase system (PTS) is a multi-protein system involved in the regulation of a variety of metabolic and transcriptional processes. The PTS catalyzes the phosphorylation of incoming sugar substrates concomitant with their translocation across the cell membrane. The general mechanism of the PTS is the following: a phosphoryl group from phosphoenolpyruvate (PEP) is transferred to enzyme-I (EI) of PTS which in turn transfers it to a phosphoryl carrier protein (HPr). Phospho-HPr then transfers the phosphoryl group to a sugar-specific permease which consists of at least three structurally distinct domains (IIA, IIB, and IIC) [PMID: 1537788] which 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). IIB (EC: is is phosphorylated by phospho-IIA, before the phosphoryl group is transferred to the sugar substrate.

Several PTS permease families are currently recognised, namely, the (i) glucose (including glucoside), (ii) fructose (including mannitol), (iii) lactose (including N,N-diacetylchitobiose), (iv) galactitol, (v) glucitol, (vi) mannose, and (vii) l-ascorbate families [PMID: 16339738].

The IIA, IIB, and IIC domains are expressed from the mtlA gene as a single protein, also known as the mannitol PTS permease, the mtl transporter, or MtlA. MtlA is only functional as a dimer with the dimer contacts occuring between the IIC domains [PMID: 11278734]. MtlA takes up exogenous mannitol releasing the phosphate ester into the cytoplasm in preparation for oxidation to fructose-6-phosphate by the NAD-dependent mannitol-P dehydrogenase (MtlD) [PMID: 8144490]. The IIB domain fold includes a central four-stranded parallel open twisted beta-sheet flanked by alpha-helices on both sides [PMID: 10393270, PMID: 15258141]. This entry represents the component EIIB of mannitol-specific PTS systems.

GO terms

Biological Process

GO:0009401 phosphoenolpyruvate-dependent sugar phosphotransferase system

Molecular Function

GO:0022872 protein-N(PI)-phosphohistidine-mannitol phosphotransferase system transmembrane transporter activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.