TonB-dependent receptor plug domain

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TonB-dependent Receptor Plug Domain
Identifiers
Symbol Plug
Pfam PF07715
InterPro IPR012910
SCOP 1fi1
OPM family 33
OPM protein 1qfg
Available PDB structures:

1qfgA:75-181 1by5A:75-181 1qkcA:75-181 1by3A:75-181 2fcpA:75-181 1fcpA:75-181 1qjqA:75-181 1qffA:75-181 1fi1A:75-181 1xkhA:161-265 1xkwA:75-175 1nqfA:38-146 1ujwA:38-146 1nqhA:38-146 1nqeA:38-146 1nqgA:38-146 1fepA:43-163 1uxfA:39-158 1kmoA:129-244 1kmpA:129-244 1po3B:129-244 1pnzA:129-244 1po0A:129-244

TonB-dependent receptor plug domain is an independently folding subunit of the TonB-dependent receptors[1]. 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.

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[2]. 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.

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[3], CirA, FatA, FcuT, FecA[4], FhuA[5], FhuE, FepA[6], 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].

[edit] References

  1. ^ Buchanan SK, Evans RW, Ghirlando R, Oke M, Sarra R, Farnaud S, Gorringe AR (2004). "The plug domain of a neisserial TonB-dependent transporter retains structural integ rity in the absence of its transmembrane beta-barrel". FEBS Lett. 564 (3): 294-300. PMID 15111112. 
  2. ^ Kadner RJ, Chimento DP, Wiener MC (2003). "The Escherichia coli outer membrane cobalamin transporter BtuB: structural analysis of calcium and substrate binding, and identification of orthologous transport ers by sequence/structure conservation". J. Mol. Biol. 332 (5): 999-1014. PMID 14499604. 
  3. ^ Kadner RJ, Chimento DP, Wiener MC, Mohanty AK (2003). "Substrate-induced transmembrane signaling in the cobalamin transporter BtuB". Nat. Struct. Biol. 10 (5): 394-401. PMID 12652322. 
  4. ^ Deisenhofer J, Smith BS, Esser L, Chakraborty R, van der Helm D, Ferguson AD (2002). "Structural basis of gating by the outer membrane transporter FecA". Science 295 (5560): 1715 -1719. PMID 11872840. 
  5. ^ Moras D, Rosenbusch JP, Mitschler A, Rees B, Locher KP, Koebnik R, Moulinier L (1998). "Transmembrane signaling across the ligand-gated Fh uA receptor: crystal structures of free and ferrichrome-bound states reveal allosteric changes". Cell 95 (6): 771-778. PMID 9865695. 
  6. ^ Deisenhofer J, Xia D, Buchanan SK, Smith BS, Venkatramani L, Esser L, Palnitkar M, Chakraborty R, van der Helm D (1999). "Crystal structure of the outer membrane active transporter FepA from Escherichia coli". Nat. S truct. Biol. 6 (1): 56-63. PMID 9886293. 
  7. ^ Klebba PE (2003). "Three paradoxes of ferric enterobactin uptake". Front. Biosci. 8: -. PMID 12957833. 
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