TonB-dependent receptor plug domain

Pfam_box
Symbol = Plug
Name = TonB-dependent Receptor Plug Domain

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width =250
caption =
Pfam= PF07715
InterPro= IPR012910
SMART=
Prosite =
SCOP = 1fi1
TCDB =
OPM family= 33
OPM protein= 1qfg
PDB=PDB3|1qfgA:75-181 PDB3|1by5A:75-181 PDB3|1qkcA:75-181PDB3|1by3A:75-181 PDB3|2fcpA:75-181 PDB3|1fcpA:75-181PDB3|1qjqA:75-181 PDB3|1qffA:75-181 PDB3|1fi1A:75-181PDB3|1xkhA:161-265 PDB3|1xkwA:75-175 PDB3|1nqfA:38-146PDB3|1ujwA:38-146 PDB3|1nqhA:38-146 PDB3|1nqeA:38-146PDB3|1nqgA:38-146 PDB3|1fepA:43-163 PDB3|1uxfA:39-158PDB3|1kmoA:129-244 PDB3|1kmpA:129-244 PDB3|1po3B:129-244PDB3|1pnzA:129-244 PDB3|1po0A:129-244

TonB-dependent receptor plug domain is an independentlyfolding subunit of the TonB-dependent receptorscite journal |author=Buchanan SK, Evans RW, Ghirlando R, Oke M, Sarra R, Farnaud S, Gorringe AR |title=The plug domain of a neisserial TonB-dependent transporter retains structural integrity in the absence of its transmembrane beta-barrel |journal=FEBS Lett. |volume=564 |issue=3 |pages=294–300 |year=2004 |pmid=15111112 |doi=10.1016/S0014-5793(04)00196-6] . 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 spacecite journal |author=Kadner RJ, Chimento DP, Wiener MC |title=The Escherichia coli outer membrane cobalamin transporter BtuB: structural analysis of calcium and substrate binding, and identification of orthologous transporters by sequence/structure conservation |journal=J. Mol. Biol. |volume=332 |issue=5 |pages=999–1014 |year=2003 |pmid=14499604 |doi=10.1016/j.jmb.2003.07.005] . These substrates are either poorly permeable through the porin channels or are encountered atvery 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 BtuBcite journal |author=Kadner RJ, Chimento DP, Wiener MC, Mohanty AK |title=Substrate-induced transmembrane signaling in the cobalamin transporter BtuB |journal=Nat. Struct. Biol. |volume=10 |issue=5 |pages=394–401 |year=2003 |pmid=12652322 |doi=10.1038/nsb914] , CirA, FatA, FcuT, FecAcite journal |author=Deisenhofer J, Smith BS, Esser L, Chakraborty R, van der Helm D, Ferguson AD |title=Structural basis of gating by the outer membrane transporter FecA |journal=Science |volume=295 |issue=5560 |pages=1715-1719 |year=2002 |pmid=11872840 |doi=10.1126/science.1067313] , FhuAcite journal |author=Moras D, Rosenbusch JP, Mitschler A, Rees B, Locher KP, Koebnik R, Moulinier L |title=Transmembrane signaling across the ligand-gated FhuA receptor: crystal structures of free and ferrichrome-bound states reveal allosteric changes |journal=Cell |volume=95 |issue=6 |pages=771–778 |year=1998 |pmid=9865695 |doi=10.1016/S0092-8674(00)81700-6] , FhuE, FepAcite journal
author=Deisenhofer J, Xia D, Buchanan SK, Smith BS, Venkatramani L, Esser L, Palnitkar M, Chakraborty R, van der Helm D |title=Crystal structure of the outer membrane active transporter FepA from Escherichia coli |journal=Nat. Struct. Biol. |volume=6 |issue=1 |pages=56–63 |year=1999 |pmid=9886293 |doi=10.1038/4931] , 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-terminuscite journal |author=Klebba PE |title=Three paradoxes of ferric enterobactin uptake |journal=Front. Biosci. |volume=8 |issue= |pages=- |year=2003 |pmid=12957833 |doi=10.2741/1233] .

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