PROSITE documentation PDOC50983
Iron siderophore/cobalamin periplasmic-binding domain profile


ATP binding cassette (ABC) transporters are a ubiquitous family of importer and exporter proteins that consist of two α-helical transmembrane (TM) domains, which form a translocation pathway, and two cytoplasmic ABC domains, which power the transport reaction through binding and hydrolysis of ATP (see <PDOC00364>). In addition most bacterial importers employs a periplasmic substrate-binding protein (PBP) that delivers the ligand to the extracellular gate of the TM domains. These proteins bind their substrates selectively and with high affinity, which is thought to ensure the specificity of the transport reaction. Binding proteins in Gram-negative bacteria are present within the periplasm, whereas those in Gram-positive bacteria are tethered to the cell membrane via the acylation of a cysteine residue that is an integral component of a lipoprotein signal sequence. The cobalamin (vitamin B12) and the iron transport systems share many common attributes and probably evolved from the same origin [1,2,3,4].

The structure of the periplasmic-binding domain is composed of two subdomains, each consisting of a central β-sheet and surrounding α-helices, linked by a rigid α-helix (see <PDB:1N4A>). The substrate binding site is located in a cleft between the two α/β subdomains [5].

Some protein known to contain an iron siderophore/cobalamin periplasmic-binding domain are listed below:

  • Escherichia coli vitamin B12 transport protein btuF. It is the periplasmic binding protein for the vitamin B12 transporter btuCD.
  • Escherichia coli ferrichrome-binding periplasmic protein (fhuD). It binds iron(III)-hydroxamates.
  • Staphylococcus aureus ferric hydroxamate receptor 2 (fhuD2).
  • Escherichia coli ferrienterobactin-binding periplasmic protein fepB. It binds ferrienterobactin; part of the binding-protein-dependent transport system for uptake of ferrienterobactin.
  • Vibrio cholerae periplasmic binding protein (viuP).
  • Escherichia coli iron(III) dicitrate-binding periplasmic protein (fecB). It binds citrate-dependent iron(III); part of the binding-protein-dependent transport system for uptake of citrate-dependent iron(III).
  • Erwinia chrysanthemi achromobactin-binding periplasmic protein (cbrA). It binds citrate-or chloride-dependent iron(III); part of the binding-protein- dependent transport system cbrABCD for uptake of the siderophore achromobactin.
  • Yersinia pestis hemin-binding periplasmic protein (hmuT).

The profile we developed covers the entire iron siderophore/cobalamin periplasmic-binding domain.

Last update:

April 2004 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

FE_B12_PBP, PS50983; Iron siderophore/cobalamin periplasmic-binding domain profile  (MATRIX)


1AuthorsBorths E.L. Locher K.P. Lee A.T. Rees D.C.
TitleThe structure of Escherichia coli BtuF and binding to its cognate ATP binding cassette transporter.
SourceProc. Natl. Acad. Sci. U.S.A. 99:16642-16647(2002).
PubMed ID12475936

2AuthorsSebulsky M.T. Shilton B.H. Speziali C.D. Heinrichs D.E.
TitleThe role of FhuD2 in iron(III)-hydroxamate transport in Staphylococcus aureus. Demonstration that FhuD2 binds iron(III)-hydroxamates but with minimal conformational change and implication of mutations on transport.
SourceJ. Biol. Chem. 278:49890-49900(2003).
PubMed ID14514690

3AuthorsStaudenmaier H. Van Hove B. Yaraghi Z. Braun V.
TitleNucleotide sequences of the fecBCDE genes and locations of the proteins suggest a periplasmic-binding-protein-dependent transport mechanism for iron(III) dicitrate in Escherichia coli.
SourceJ. Bacteriol. 171:2626-2633(1989).
PubMed ID2651410

4AuthorsKoester W.L. Actis L.A. Waldbeser L.S. Tolmasky M.E. Crosa J.H.
SourceJ. Biol. Chem. 266:23829-23833(1991).

5AuthorsKarpowich N.K. Huang H.H. Smith P.C. Hunt J.F.
TitleCrystal structures of the BtuF periplasmic-binding protein for vitamin B12 suggest a functionally important reduction in protein mobility upon ligand binding.
SourceJ. Biol. Chem. 278:8429-8434(2003).
PubMed ID12468528

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