Letunic et al. (2017) Nucleic Acids Res doi: 10.1093/nar/gkx922
Letunic et al. (2020) Nucleic Acids Res doi: 10.1093/nar/gkaa937

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STN Secretin and TonB N terminus short domain

SMART accession number:	SM00965
Description:	This is a short domain found at the N-terminus of the Secretins of the bacterial type II/III secretory system as well as the TonB-dependent receptor proteins. These proteins are involved in TonB-dependent active uptake of selective substrates.
Interpro abstract (IPR011662):	This is a short domain found at the N terminus of the Secretins of the bacterial type II/III secretory system, as well as the TonB-dependent receptor proteins. These proteins are involved in TonB-dependent active uptake of selective substrates.
GO component:	outer membrane (GO:0019867)
Family alignment:	View or CHROMA formatHMM/Web logoCLUSTALW formatMSF formatFASTA formatPIR format

There are 33017 STN domains in 32858 proteins in SMART's nrdb database.

Click on the following links for more information.

• Evolution (species in which this domain is found)

• Taxonomic distribution of proteins containing STN domain.

  This tree includes only several representative species. The complete taxonomic breakdown of all proteins with STN domain is also avaliable.

  Click on the protein counts, or double click on taxonomic names to display all proteins containing STN domain in the selected taxonomic class.

• Cellular role (predicted cellular role)

• Cellular role: transport
  

• Literature (relevant references for this domain)

• Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

  • Khursigara CM, De Crescenzo G, Pawelek PD, Coulton JW
  • Deletion of the proline-rich region of TonB disrupts formation of a 2:1complex with FhuA, an outer membrane receptor of Escherichia coli.
  • Protein Sci. 2005; 14: 1266-73
  • Display abstract

  • TonB protein of Escherichia coli couples the electrochemical potential ofthe cytoplasmic membrane (CM) to active transport of iron-siderophores andvitamin B(12) across the outer membrane (OM). TonB interacts with OMreceptors and transduces conformationally stored energy. Energy fortransport is provided by the proton motive force through ExbB and ExbD,which form a ternary complex with TonB in the CM. TonB contains threedistinct domains: an N-terminal signal/anchor sequence, a C-terminaldomain, and a proline-rich region. The proline-rich region was proposed toextend TonB's structure across the periplasm, allowing it to contactspatially distant OM receptors. Having previously identified a 2:1stoichiometry for the complex of full-length (FL) TonB and the OM receptorFhuA, we now demonstrate that deletion of the proline-rich region of TonB(TonBDelta66-100) prevents formation of the 2:1 complex. Sedimentationvelocity analytical ultracentrifugation of TonBDelta66-100 with FhuArevealed that a 1:1 TonB-FhuA complex is formed. Interactions betweenTonBDelta66-100 and FhuA were assessed by surface plasmon resonance, andtheir affinities were determined to be similar to those of TonB (FL)-FhuA.Presence of the FhuA-specific siderophore ferricrocin altered neitherstoichiometry nor affinity of interaction, leading to our conclusion thatthe proline-rich region in TonB is important in forming a 2:1high-affinity TonB-FhuA complex in vitro. Furthermore,TonBDelta66-100-FhuADelta21-128 interactions demonstrated that the corkregion of the OM receptor was also important in forming a complex.Together, these results demonstrate a novel function of the proline-richregion of TonB in mediating TonB-TonB interactions within the TonB-FhuAcomplex.

  • Ramer SW, Bieber D, Schoolnik GK
  • BfpB, an outer membrane lipoprotein required for the biogenesis ofbundle-forming pili in enteropathogenic Escherichia coli.
  • J Bacteriol. 1996; 178: 6555-63
  • Display abstract

  • The bundle-forming pili (BFP) of enteropathogenic Escherichia coli arebelieved to play a role in pathogenesis by causing the formation ofbacterial microcolonies that bind epithelial surfaces of the smallintestine. This in vivo process is mimicked in vitro by theautoaggregation and localized adherence phenotypes. Expression of BFP, amember of the type IV pilus family, requires the enteroadherence factor(EAF) plasmid, which contains bfpA, the gene that encodes the principalstructural subunit of BFP. Immediately downstream of bfpA are 13 openreading frames transcribed in the same direction as bfpA; together withbfpA, these compose the bfp gene cluster. Disruption of bfpB, the secondopen reading frame downstream of bfpA, was performed by allelic exchange.The resulting mutant, B171-8deltaB, did not exhibit the autoaggregation orlocalized adherence phenotype or produce BFP filaments. Thus, BfpB isrequired for pilus biogenesis. However, BfpA was produced at wild-typelevels and processed normally by B171-8deltaB, indicating that BfpB actsat a step in the BFP biogenic pathway after production and processing ofthe structural subunit. Biochemical and cell fractionation studies showedthat BfpB is a 58-kDa lipoprotein that is located primarily in the outermembrane. Assays of bfpA and bfpB mRNAs and protein expression showed thatboth genes are cotranscribed as part of an environmentally responsiveoperon that is regulated by growth phase and ammonium.

• Structure (3D structures containing this domain)

• 3D Structures of STN domains in PDB

  PDB code	Main view	Title
  1kmo		Crystal structure of the Outer Membrane Transporter FecA
  1kmp		Crystal structure of the Outer Membrane Transporter FecA Complexed with Ferric Citrate
  1pnz		Crystal structure of ferric citrate transporter FecA in the unliganded form
  1po0		Crystal structure of ferric citrate transporter FecA in complex with iron-free citrate
  1po3		Crystal structure of ferric citrate transporter FecA in complex with ferric citrate
  1zzv		Solution NMR Structure of the Periplasmic Signaling Domain of the Outer Membrane Iron Transporter FecA from Escherichia coli.
  2a02		Solution NMR Structure of the Periplasmic Signaling Domain of the Outer Membrane Iron Transporter PupA from Pseudomonas putida.
  2d1u		Solution strcuture of the periplasmic signaling domain of FecA from Escherichia coli
  2iah		Crystal structure of the ferripyoverdine receptor of the outer membrane of Pseudomonas aeruginosa bound to ferripyoverdine.
  2m5j		Solution structure of the periplasmic signaling domain of HasR, a TonB-dependent outer membrane heme transporter
  2o5p		Crystal structure of the full length ferric pyoverdine outer membrane receptor FpvA of Pseudomonas aeruginosa in its apo form
  2w16		Structures of FpvA bound to heterologous pyoverdines
  2w6t		Structures of P. aeruginosa FpvA bound to heterologous pyoverdines: FpvA-Pvd(DSM50106)-Fe complex
  2w6u		Structures of P. aeruginosa FpvA bound to heterologous pyoverdines: FpvA-Pvd(G173)-Fe complex
  2w75		Structures of P. aeruginosa FpvA bound to heterologous pyoverdines: Apo-FpvA
  2w76		Structures of P. aeruginosa FpvA bound to heterologous pyoverdines: FpvA-Pvd(Pa6)-Fe complex
  2w77		Structures of P. aeruginosa FpvA bound to heterologous pyoverdines: FpvA-Pvd(Pfl18.1)-Fe complex
  2w78		Structures of P. aeruginosa FpvA bound to heterologous pyoverdines: FpvA-Pvd(ATCC13535)-Fe complex
  3csl		Structure of the Serratia marcescens hemophore receptor HasR in complex with its hemophore HasA and heme
  3csn		Structure of the Serratia marcescens hemophore receptor HasR in complex with its hemophore HasA
  3ddr		Structure of the Serratia marcescens hemophore receptor HasR-Ile671Gly mutant in complex with its hemophore HasA and heme
  3jc8		3JC8
  3jc9		3JC9
  4ar0		N0 domain of Neisseria meningitidis Pilus assembly protein PilQ
  4av2		Single particle electron microscopy of PilQ dodecameric complexes from Neisseria meningitidis.
  5c58		5C58

• Links (links to other resources describing this domain)

• PFAM	STN
  INTERPRO	IPR011662

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