Homologous Superfamily

TonB-dependent receptor, plug domain superfamily (IPR037066)

Short name: Plug_dom_sf

Overlapping entries


In Escherichia coli the TonB protein interacts with outer membrane receptor proteins that carry out high-affinity binding and energy-dependent uptake of specific substrates into the periplasmic space [PMID: 14499604]. These substrates are either poorly permeable through the porin channels or are encountered at very low concentrations. In the absence of TonB, these receptors bind their substrates but do not carry out active transport. TonB-dependent regulatory systems consist of six components: a specialised outer membrane-localized TonB-dependent receptor (TonB-dependent transducer) that interacts with its energizing TonB-ExbBD protein complex, a cytoplasmic membrane-localized anti-sigma factor and an extracytoplasmic function (ECF)-subfamily sigma factor [PMID: 15993072]. The TonB complex senses signals from outside the bacterial cell and transmits them via two membranes into the cytoplasm, leading to transcriptional activation of target genes. The proteins that are currently known or presumed to interact with TonB include BtuB [PMID: 12652322], CirA, FatA, FcuT, FecA [PMID: 11872840], FhuA [PMID: 9865695], FhuE, FepA [PMID: 9886293], FptA, HemR, IrgA, IutA, PfeA, PupA and Tbp1. The TonB protein also interacts with some colicins. Most of these proteins contain a short conserved region at their N terminus [PMID: 12957833].

This entry represents the plug domain superfamily, which has been shown to be an independently folding subunit of the TonB-dependent receptors [PMID: 15111112]. It acts as the channel gate, blocking the pore until the channel is bound by a ligand. At this point it undergoes conformational changes and opens the channel.

Contributing signatures

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