ferrichrome

Summary

Summary: A cyclic peptide consisting of three residues of delta-N-hydroxy-delta-N-acetylornithine. It acts as an iron transport agent in Ustilago sphaerogena.

Top Publications

  1. Oberegger H, Schoeser M, Zadra I, Abt B, Haas H. SREA is involved in regulation of siderophore biosynthesis, utilization and uptake in Aspergillus nidulans. Mol Microbiol. 2001;41:1077-89 pubmed
    ..amcA encodes a putative mitochondrial carrier for the siderophore precursor ornithine, indicating cross-regulation of siderophore and ornithine metabolism...
  2. Ardon O, Bussey H, Philpott C, Ward D, Davis Kaplan S, Verroneau S, et al. Identification of a Candida albicans ferrichrome transporter and its characterization by expression in Saccharomyces cerevisiae. J Biol Chem. 2001;276:43049-55 pubmed
    ..lacking endogenous siderophore transporters, we demonstrate that CaArn1p specifically mediates the uptake of ferrichrome-iron...
  3. Schwecke T, Göttling K, Durek P, Dueñas I, Käufer N, Zock Emmenthal S, et al. Nonribosomal peptide synthesis in Schizosaccharomyces pombe and the architectures of ferrichrome-type siderophore synthetases in fungi. Chembiochem. 2006;7:612-22 pubmed
    ..six thiolation domains and six condensation domains, has been shown to produce the cyclohexapeptide siderophore ferrichrome. One of the adenylation domains is truncated and contains a distorted key motif...
  4. Winterberg B, Uhlmann S, Linne U, Lessing F, Marahiel M, Eichhorn H, et al. Elucidation of the complete ferrichrome A biosynthetic pathway in Ustilago maydis. Mol Microbiol. 2010;75:1260-71 pubmed publisher
    ..To acquire iron, the basidiomycete Ustilago maydis synthesizes the iron-chelating siderophores ferrichrome and ferrichrome A...
  5. Hanks T, Liu M, McClure M, Lei B. ABC transporter FtsABCD of Streptococcus pyogenes mediates uptake of ferric ferrichrome. BMC Microbiol. 2005;5:62 pubmed
    ..MtsABC and HtsABC are believed to take up ferric (Fe3+) and manganese ions and heme, respectively, while the specificity of FtsABCD is unknown...
  6. Cheng W, Li Q, Jiang Y, Zhou C, Chen Y. Structures of Streptococcus pneumoniae PiaA and its complex with ferrichrome reveal insights into the substrate binding and release of high affinity iron transporters. PLoS ONE. 2013;8:e71451 pubmed publisher
    ..The high affinity towards ferrichrome enables PiaA to capture iron at a very low concentration in the host...
  7. Llamas M, Sparrius M, Kloet R, Jimenez C, Vandenbroucke Grauls C, Bitter W. The heterologous siderophores ferrioxamine B and ferrichrome activate signaling pathways in Pseudomonas aeruginosa. J Bacteriol. 2006;188:1882-91 pubmed
    ..Two of them are only produced in the presence of the hydroxamate siderophores ferrioxamine B and ferrichrome. Regulation of their synthesis is affected by both iron and the presence of a cognate siderophore...
  8. Kim Y, Lampert S, Philpott C. A receptor domain controls the intracellular sorting of the ferrichrome transporter, ARN1. EMBO J. 2005;24:952-62 pubmed
    The Saccharomyces cerevisiae transporter Arn1p takes up the ferric-siderophore ferrichrome, and extracellular ferrichrome dramatically influences the intracellular trafficking of Arn1p...
  9. Matzanke B, Bohnke R, Möllmann U, Reissbrodt R, Schunemann V, Trautwein A. Iron uptake and intracellular metal transfer in mycobacteria mediated by xenosiderophores. Biometals. 1997;10:193-203 pubmed
    ..Mycobactin has merely a transient role. The ultimate storage compound is an E. coli-type bacterioferritin, in which over 90% of cellular iron is located...

More Information

Publications62

  1. Clarke T, Braun V, Winkelmann G, Tari L, Vogel H. X-ray crystallographic structures of the Escherichia coli periplasmic protein FhuD bound to hydroxamate-type siderophores and the antibiotic albomycin. J Biol Chem. 2002;277:13966-72 pubmed
  2. Carlton T, Sullivan J, Stuart G, Hutt K, Lamont I, Ronson C. Ferrichrome utilization in a mesorhizobial population: microevolution of a three-locus system. Environ Microbiol. 2007;9:2923-32 pubmed
    The ability to utilize the siderophore ferrichrome as an iron source was found to be a variable trait in a field population of mesorhizobia...
  3. Yuan W, Gentil G, Budde A, Leong S. Characterization of the Ustilago maydis sid2 gene, encoding a multidomain peptide synthetase in the ferrichrome biosynthetic gene cluster. J Bacteriol. 2001;183:4040-51 pubmed
    ..acquires and transports ferric ion by producing the extracellular, cyclic peptide, hydroxamate siderophores ferrichrome and ferrichrome A...
  4. Kim Y, Deng Y, Philpott C. GGA2- and ubiquitin-dependent trafficking of Arn1, the ferrichrome transporter of Saccharomyces cerevisiae. Mol Biol Cell. 2007;18:1790-802 pubmed
    The intracellular trafficking of Arn1, a ferrichrome transporter in Saccharomyces cerevisiae, is controlled in part by the binding of ferrichrome to the transporter...
  5. Kim Y, Yun C, Philpott C. Ferrichrome induces endosome to plasma membrane cycling of the ferrichrome transporter, Arn1p, in Saccharomyces cerevisiae. EMBO J. 2002;21:3632-42 pubmed
    ..Here we present evidence that, in the absence of its specific substrate, ferrichrome, Arn1p is sorted directly from the Golgi to the endosomal compartment and does not cycle to the plasma membrane...
  6. Seifert M, Nairz M, Schroll A, Schrettl M, Haas H, Weiss G. Effects of the Aspergillus fumigatus siderophore systems on the regulation of macrophage immune effector pathways and iron homeostasis. Immunobiology. 2008;213:767-78 pubmed publisher
    ..fumigatus affects the regulation of macrophage iron homeostasis and innate immune effector pathways via its siderophore system. The changes in immune response may be a consequence of macrophage iron restriction...
  7. Clarke T, Ku S, Dougan D, Vogel H, Tari L. The structure of the ferric siderophore binding protein FhuD complexed with gallichrome. Nat Struct Biol. 2000;7:287-91 pubmed
    ..FhuD is a soluble periplasmic binding protein that transports ferrichrome and other hydroxamate siderophores...
  8. Cuív P, Keogh D, Clarke P, O CONNELL M. The hmuUV genes of Sinorhizobium meliloti 2011 encode the permease and ATPase components of an ABC transport system for the utilization of both haem and the hydroxamate siderophores, ferrichrome and ferrioxamine B. Mol Microbiol. 2008;70:1261-73 pubmed publisher
    ..meliloti can also acquire iron from xenosiderophores and the genes encoding the outer membrane receptors for ferrichrome and ferrioxamine B, fhuA1 and fhuA2, respectively, were identified...
  9. Hissen A, Wan A, Warwas M, Pinto L, Moore M. The Aspergillus fumigatus siderophore biosynthetic gene sidA, encoding L-ornithine N5-oxygenase, is required for virulence. Infect Immun. 2005;73:5493-503 pubmed
    ..Unlike the wild-type and rescued strains, the DeltasidA strain was avirulent in a mouse model of invasive aspergillosis, indicating that sidA is necessary for A. fumigatus virulence...
  10. Cuív P, Keogh D, Clarke P, O CONNELL M. FoxB of Pseudomonas aeruginosa functions in the utilization of the xenosiderophores ferrichrome, ferrioxamine B, and schizokinen: evidence for transport redundancy at the inner membrane. J Bacteriol. 2007;189:284-7 pubmed
    ..of Pseudomonas aeruginosa in mutants of Sinorhizobium meliloti that are defective in the utilization of ferrichrome, ferrioxamine B, and schizokinen resulted in the restoration of siderophore utilization...
  11. Funahashi T, Tanabe T, Shiuchi K, Nakao H, Yamamoto S. Identification and characterization of genes required for utilization of desferri-ferrichrome and aerobactin in Vibrio parahaemolyticus. Biol Pharm Bull. 2009;32:359-65 pubmed
    ..a causative agent of seafood-related gastroenteritis, we found that this species utilizes desferri-ferrichrome for growth as a heterologous siderophore (a siderophore produced by other bacteria and fungi) under iron-..
  12. Rohrbach M, Braun V, Koster W. Ferrichrome transport in Escherichia coli K-12: altered substrate specificity of mutated periplasmic FhuD and interaction of FhuD with the integral membrane protein FhuB. J Bacteriol. 1995;177:7186-93 pubmed
    ..4 microM for ferric aerobactin, 1.0 microM for ferrichrome, 0.3 microM for ferric coprogen, and 5.4 microM for the antibiotic albomycin...
  13. Pramanik A, Stroeher U, Krejci J, Standish A, Bohn E, Paton J, et al. Albomycin is an effective antibiotic, as exemplified with Yersinia enterocolitica and Streptococcus pneumoniae. Int J Med Microbiol. 2007;297:459-69 pubmed
    ..The ferrichrome transport system serves as a Trojan horse to get albomycin into bacteria.
  14. Mikael L, Srikumar R, Coulton J, Jacques M. fhuA of Actinobacillus pleuropneumoniae encodes a ferrichrome receptor but is not regulated by iron. Infect Immun. 2003;71:2911-5 pubmed
    ..Actinobacillus pleuropneumoniae possesses a 75-kDa outer membrane protein (OMP), FhuA, the receptor for ferrichrome, a hydroxamate-type siderophore. Polyclonal serum to FhuA reacted with OMP preparations from 12 serotypes of A...
  15. Rajendran G, Mistry S, Desai A, Archana G. Functional expression of Escherichia coli fhuA gene in Rhizobium spp. of Cajanus cajan provides growth advantage in presence of Fe3+: ferrichrome as iron source. Arch Microbiol. 2007;187:257-64 pubmed
    Cajanus cajan rhizobial isolates were found to be unable to utilize iron bound to ferrichrome, desferrioxamine B or rhodotorulic acid, all being hydroxamate type siderophores...
  16. Faraldo Gómez J, Smith G, Sansom M. Molecular dynamics simulations of the bacterial outer membrane protein FhuA: a comparative study of the ferrichrome-free and bound states. Biophys J. 2003;85:1406-20 pubmed
    ..Its primary function is to provide a binding site on the outer membrane surface for siderophores, such as ferrichrome, and subsequently to facilitate their energy-dependent transport across the membrane, presumably powered by the ..
  17. Eisendle M, Oberegger H, Zadra I, Haas H. The siderophore system is essential for viability of Aspergillus nidulans: functional analysis of two genes encoding l-ornithine N 5-monooxygenase (sidA) and a non-ribosomal peptide synthetase (sidC). Mol Microbiol. 2003;49:359-75 pubmed
    ..This indicates that the lack of this cellular iron storage compound causes oxidative stress. Moreover, ferricrocin biosynthesis was found to be crucial for efficient conidiation...
  18. Rogers M, Sexton J, DeCastro G, Calderwood S. Identification of an operon required for ferrichrome iron utilization in Vibrio cholerae. J Bacteriol. 2000;182:2350-3 pubmed
    ..the identification of seven independent fusion strains, each of which was deficient in the ability to utilize ferrichrome as a sole iron source for growth in a plate bioassay and had an insertion in genes encoding products homologous ..
  19. Kim J, Kim H, Heo D, Chang M, Baek I, Yun C. FgEnd1 is a putative component of the endocytic machinery and mediates ferrichrome uptake in F. graminearum. Curr Genet. 2009;55:593-600 pubmed publisher
    ..Furthermore, fgend1 deletion strain of F. graminearum showed lower ferrichrome (FC) uptake activity than wild-type F. graminearum, and the same rate as LatA-treated cells...
  20. Wallner A, Blatzer M, Schrettl M, Sarg B, Lindner H, Haas H. Ferricrocin, a siderophore involved in intra- and transcellular iron distribution in Aspergillus fumigatus. Appl Environ Microbiol. 2009;75:4194-6 pubmed publisher
    ..Thus, ferricrocin represents the first intracellular iron transporter identified in any organism...
  21. Hannauer M, Barda Y, Mislin G, Shanzer A, Schalk I. The ferrichrome uptake pathway in Pseudomonas aeruginosa involves an iron release mechanism with acylation of the siderophore and recycling of the modified desferrichrome. J Bacteriol. 2010;192:1212-20 pubmed publisher
    ..In this work, we have investigated the iron uptake in P. aeruginosa PAO1 by the heterologous ferrichrome siderophore...
  22. Killmann H, Gestwa G. Determination of ferrichrome binding to the FhuA outer membrane transport protein, periplasmic accumulation of ferrichrome, or transport of ferrichrome into cells using a three-layer oil technique. Anal Biochem. 2002;310:55-60 pubmed
    A new method for the determination of ferrichrome binding to the FhuA transporter in the Escherichia coli outer membrane, ferrichrome accumulation in the periplasmic space, and ferrichrome transport into the cytoplasm was developed...
  23. Moore R, Kim Y, Philpott C. The mechanism of ferrichrome transport through Arn1p and its metabolism in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A. 2003;100:5664-9 pubmed
    ..Here we describe how ferrichrome, a siderophore of the hydroxamate class, is taken up by Arn1p...
  24. Schrettl M, Kim H, Eisendle M, Kragl C, Nierman W, Heinekamp T, et al. SreA-mediated iron regulation in Aspergillus fumigatus. Mol Microbiol. 2008;70:27-43 pubmed publisher
    ..As all detrimental effects of sreA disruption are restricted to iron-replete conditions these data underscore that A. fumigatus faces iron-depleted conditions during infection...
  25. Heymann P, Ernst J, Winkelmann G. Identification and substrate specificity of a ferrichrome-type siderophore transporter (Arn1p) in Saccharomyces cerevisiae. FEMS Microbiol Lett. 2000;186:221-7 pubmed
    ..A strain possessing a disruption in the ARN1 gene was unable to transport ferrirubin, ferrirhodin and also ferrichrome A, indicating that the encoded transporter recognizes anhydromevalonyl and the structurally-related ..
  26. Coulton J, Mason P, Allatt D. fhuC and fhuD genes for iron (III)-ferrichrome transport into Escherichia coli K-12. J Bacteriol. 1987;169:3844-9 pubmed
    ..Because the FhuD protein contains a typical signal sequence of 30 amino acids at the amino terminus and displays characteristics of a soluble protein, it may be exported into the periplasm...
  27. Welzel K, Eisfeld K, Antelo L, Anke T, Anke H. Characterization of the ferrichrome A biosynthetic gene cluster in the homobasidiomycete Omphalotus olearius. FEMS Microbiol Lett. 2005;249:157-63 pubmed
    Under iron deprivation Omphalotus olearius was found to produce the hydroxamate siderophore ferrichrome A...
  28. Yun C, Tiedeman J, Moore R, Philpott C. Siderophore-iron uptake in saccharomyces cerevisiae. Identification of ferrichrome and fusarinine transporters. J Biol Chem. 2000;275:16354-9 pubmed
    ..Here we report that ARN family members facilitated the uptake of iron from the trihydroxamate siderophores ferrichrome, ferrichrome A, and triacetylfusarinine C...
  29. Coulton J, Mason P, Cameron D, Carmel G, Jean R, Rode H. Protein fusions of beta-galactosidase to the ferrichrome-iron receptor of Escherichia coli K-12. J Bacteriol. 1986;165:181-92 pubmed
    The fusion-generating phage lambda plac Mu1 was used to produce fusions of lacZ to fhuA, the gene encoding the ferrichrome-iron receptor (FhuA protein) in the outer membrane of Escherichia coli K-12...
  30. Mercier A, Labbe S. Iron-dependent remodeling of fungal metabolic pathways associated with ferrichrome biosynthesis. Appl Environ Microbiol. 2010;76:3806-17 pubmed publisher
    The fission yeast Schizosaccharomyces pombe excretes and accumulates the hydroxamate-type siderophore ferrichrome. The sib1(+) and sib2(+) genes encode, respectively, a siderophore synthetase and an l-ornithine N(5)-oxygenase that ..
  31. Eisendle M, Schrettl M, Kragl C, Muller D, Illmer P, Haas H. The intracellular siderophore ferricrocin is involved in iron storage, oxidative-stress resistance, germination, and sexual development in Aspergillus nidulans. Eukaryot Cell. 2006;5:1596-603 pubmed
  32. Oberegger H, Eisendle M, Schrettl M, Graessle S, Haas H. 4'-phosphopantetheinyl transferase-encoding npgA is essential for siderophore biosynthesis in Aspergillus nidulans. Curr Genet. 2003;44:211-5 pubmed
  33. Schrettl M, Winkelmann G, Haas H. Ferrichrome in Schizosaccharomyces pombe--an iron transport and iron storage compound. Biometals. 2004;17:647-54 pubmed
    ..pombe excretes and accumulates intracellularly the hydroxamate-type siderophore ferrichrome. Under iron-limiting conditions, the cellular ferrichrome pool was present in the desferri-form, while under ..
  34. Locher K, Rees B, Koebnik R, Mitschler A, Moulinier L, Rosenbusch J, et al. Transmembrane signaling across the ligand-gated FhuA receptor: crystal structures of free and ferrichrome-bound states reveal allosteric changes. Cell. 1998;95:771-8 pubmed
    FhuA protein facilitates ligand-gated transport of ferrichrome-bound iron across Escherichia coli outer membranes. X-ray analysis at 2.7 A resolution reveals two distinct conformations in the presence and absence of ferrichrome...
  35. Pramanik A, Braun V. Albomycin uptake via a ferric hydroxamate transport system of Streptococcus pneumoniae R6. J Bacteriol. 2006;188:3878-86 pubmed
    ..pneumoniae. Albomycin was transported via the system that transports the ferric hydroxamates ferrichrome and ferrioxamine B. These two ferric hydroxamates antagonized the growth inhibition by albomycin and salmycin...
  36. Nelson M, Carrano C, Szaniszlo P. Identification of the ferrioxamine B receptor, FoxB, in Escherichia coli K12. Biometals. 1992;5:37-46 pubmed
    ..Photolysis of this analog inhibited uptake of [59Fe]ferrioxamine B but not [59Fe]ferrichrome. Conversely, photolysis of the p-azidobenzoyl analog of coprogen B inhibited uptake of [59Fe]coprogen but not [..
  37. Li H, Li N, Xu Q, Xiao C, Wang H, Guo Z, et al. Lipoprotein FtsB in Streptococcus pyogenes binds ferrichrome in two steps with residues Tyr137 and Trp204 as critical ligands. PLoS ONE. 2013;8:e65682 pubmed publisher
    Lipoprotein FtsB is a component of the FtsABCD transporter that is responsible for ferrichrome binding and uptake in the Gram-positive pathogen Streptococcus pyogenes...
  38. Yasmin S, Abt B, Schrettl M, Moussa T, Werner E, Haas H. The interplay between iron and zinc metabolism in Aspergillus fumigatus. Fungal Genet Biol. 2009;46:707-13 pubmed publisher
    ..Taken together, these data demonstrate a fine tuned coordination of zinc and iron metabolism in A. fumigatus...
  39. Vajrala N, Sayavedra Soto L, Bottomley P, Arp D. Role of Nitrosomonas europaea NitABC iron transporter in the uptake of Fe3+-siderophore complexes. Arch Microbiol. 2010;192:899-908 pubmed publisher
    ..was unable to grow in Fe-limited media containing either the hydroxamate-type siderophores, ferrioxamine and ferrichrome or the mixed-chelating type siderophore, pyoverdine. Exposure of N...
  40. Koster W, Braun V. Iron (III) hydroxamate transport into Escherichia coli. Substrate binding to the periplasmic FhuD protein. J Biol Chem. 1990;265:21407-10 pubmed
    ..In support of this notion we demonstrate specific binding of the Fe3+ hydroxamate compounds ferrichrome, aerobactin, and coprogen, which are transported via the Fhu system, to the periplasmic FhuD protein, and no ..
  41. Braun V. The structurally related exbB and tolQ genes are interchangeable in conferring tonB-dependent colicin, bacteriophage, and albomycin sensitivity. J Bacteriol. 1989;171:6387-90 pubmed
    ..Cells carrying mutations in exbB were partially tolerant to colicins B, D, and M and became fully tolerant by the introduction of tolQ mutations. This suggested involvement of both exbB and tolQ in tonB-dependent uptake...
  42. Beall B, Hoenes T. An iron-regulated outer-membrane protein specific to Bordetella bronchiseptica and homologous to ferric siderophore receptors. Microbiology. 1997;143 ( Pt 1):135-45 pubmed
    ..bronchiseptica and B. pertussis. In addition, the hydroxamate siderophores ferrichrome and desferrioxamine B, and the iron source haemin were shown to be utilized independently of bfeA and bfrA in B...
  43. Endriss F, Braun V. Loop deletions indicate regions important for FhuA transport and receptor functions in Escherichia coli. J Bacteriol. 2004;186:4818-23 pubmed
    ..Deletion of loop 3 or 11 inactivated ferrichrome transport activity...
  44. Nicholson M, Beall B. Disruption of tonB in Bordetella bronchiseptica and Bordetella pertussis prevents utilization of ferric siderophores, haemin and haemoglobin as iron sources. Microbiology. 1999;145 ( Pt 9):2453-61 pubmed
    ..resulted in inability to grow in iron-limiting media, and inability to utilize alcaligin, enterobactin, ferrichrome, desferroxamine B, haemin and haemoglobin. Although it was not possible to inactivate tonB in a clinical B...
  45. Gendron R, Grenier D, Sorsa T, Uitto V, Mayrand D. Effect of microbial siderophores on matrix metalloproteinase-2 activity. J Periodontal Res. 1999;34:50-3 pubmed
    ..Degradation of gelatin was monitored by SDS-PAGE and Coomassie blue staining. Ferrichrome, rhodotorulic acid, desferoxamine mesylate and 2,3-dihydroxybenzoic acid were found to inhibit the MMP-2 ..
  46. Ferguson A, Hofmann E, Coulton J, Diederichs K, Welte W. Siderophore-mediated iron transport: crystal structure of FhuA with bound lipopolysaccharide. Science. 1998;282:2215-20 pubmed
    FhuA, the receptor for ferrichrome-iron in Escherichia coli, is a member of a family of integral outer membrane proteins, which, together with the energy-transducing protein TonB, mediate the active transport of ferric siderophores ..
  47. Ferguson A, Braun V, Fiedler H, Coulton J, Diederichs K, Welte W. Crystal structure of the antibiotic albomycin in complex with the outer membrane transporter FhuA. Protein Sci. 2000;9:956-63 pubmed
  48. Bonhivers M, Desmadril M, Moeck G, Boulanger P, Colomer Pallas A, Letellier L. Stability studies of FhuA, a two-domain outer membrane protein from Escherichia coli. Biochemistry. 2001;40:2606-13 pubmed
    FhuA (MM 78.9 kDa) is an Escherichia coli outer membrane protein that transports iron coupled to ferrichrome and is the receptor for a number of bacteriophages and protein antibiotics...
  49. Wu H, Santoni Rugiu E, Ralfkiaer E, Porse B, Moser C, Høiby N, et al. Lipocalin 2 is protective against E. coli pneumonia. Respir Res. 2010;11:96 pubmed publisher
    ..coli is rare despite a frequent exposure to this commensal bacterium. Lipocalin 2 is an effector molecule of the innate immune system and could therefore play a role in hindering growth of E. coli in the lungs...
  50. Killmann H, Braun M, Herrmann C, Braun V. FhuA barrel-cork hybrids are active transporters and receptors. J Bacteriol. 2001;183:3476-87 pubmed
    ..agglomerans protein, transported ferrichrome and albomycin...
  51. Guo Y, Au W, Shakoury Elizeh M, Protchenko O, Basrai M, Prinz W, et al. Phosphatidylserine is involved in the ferrichrome-induced plasma membrane trafficking of Arn1 in Saccharomyces cerevisiae. J Biol Chem. 2010;285:39564-73 pubmed publisher
    Arn1 is an integral membrane protein that mediates the uptake of ferrichrome, an important nutritional source of iron, in Saccharomyces cerevisiae...
  52. Howard S, Herrmann C, Stratilo C, Braun V. In vivo synthesis of the periplasmic domain of TonB inhibits transport through the FecA and FhuA iron siderophore transporters of Escherichia coli. J Bacteriol. 2001;183:5885-95 pubmed
    ..Overexpressed TonB(33-239), TonB(103-239), and TonB(122-239) fragments inhibited transport of ferrichrome by FhuA and of ferric citrate by FecA, transcriptional induction of the fecABCDE transport genes by FecA, ..
  53. Anton M, Heller K. Functional analysis of a C-terminally altered TonB protein of Escherichia coli. Gene. 1991;105:23-9 pubmed
    ..The possibility is discussed that the C-terminal hydrophobic region is involved in the intramolecular interaction rather than in the membrane association of TonB...