H
IPR037066

TonB-dependent receptor, plug domain superfamily

InterPro entry
Short namePlug_dom_sf
Overlapping entries
 

Description

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
[3]
. 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
[6]
. 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
[1]
, CirA, FatA, FcuT, FecA
[8]
, FhuA
[2]
, FhuE, FepA
[5]
, 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
[7]
.

This entry represents the plug domain superfamily, which has been shown to be an independently folding subunit of the TonB-dependent receptors
[4]
. 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.

References

1.Substrate-induced transmembrane signaling in the cobalamin transporter BtuB. Chimento DP, Mohanty AK, Kadner RJ, Wiener MC. Nat. Struct. Biol. 10, 394-401, (2003). View articlePMID: 12652322

2.Transmembrane signaling across the ligand-gated FhuA receptor: crystal structures of free and ferrichrome-bound states reveal allosteric changes. Locher KP, Rees B, Koebnik R, Mitschler A, Moulinier L, Rosenbusch JP, Moras D. Cell 95, 771-8, (1998). View articlePMID: 9865695

3.The Escherichia coli outer membrane cobalamin transporter BtuB: structural analysis of calcium and substrate binding, and identification of orthologous transporters by sequence/structure conservation. Chimento DP, Kadner RJ, Wiener MC. J. Mol. Biol. 332, 999-1014, (2003). View articlePMID: 14499604

4.The plug domain of a neisserial TonB-dependent transporter retains structural integrity in the absence of its transmembrane beta-barrel. Oke M, Sarra R, Ghirlando R, Farnaud S, Gorringe AR, Evans RW, Buchanan SK. FEBS Lett. 564, 294-300, (2004). View articlePMID: 15111112

5.Crystal structure of the outer membrane active transporter FepA from Escherichia coli. Buchanan SK, Smith BS, Venkatramani L, Xia D, Esser L, Palnitkar M, Chakraborty R, van der Helm D, Deisenhofer J. Nat. Struct. Biol. 6, 56-63, (1999). View articlePMID: 9886293

6.TonB-dependent trans-envelope signalling: the exception or the rule? Koebnik R. Trends Microbiol. 13, 343-7, (2005). View articlePMID: 15993072

7.Three paradoxes of ferric enterobactin uptake. Klebba PE. Front. Biosci. 8, s1422-36, (2003). PMID: 12957833

8.Structural basis of gating by the outer membrane transporter FecA. Ferguson AD, Chakraborty R, Smith BS, Esser L, van der Helm D, Deisenhofer J. Science 295, 1715-9, (2002). View articlePMID: 11872840

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