|Gene:||efeB||Accession Numbers: EG11735 (EcoCyc), b1019, ECK1009|
Component of: EfeU/EfeO/EfeB ferrous iron transporter; cryptic (extended summary available)
Subunit composition of
EfeB dimer = [EfeB]2
heme-containing peroxidase/deferrochelatase = EfeB
EfeB is a heme-containing component of the cryptic EfeUOB ferrous iron transporter.
Due to the lack of an outer membrane receptor for heme, E. coli K-12 is unable to utilize heme as a source of iron [Sasarman68, McConville79]. However, expression of the heme receptor protein HasR from Serratia marcescens enables utilization of heme as a source of iron. This requires the presence of either the Dpp dipeptide ABC transporter or of the EfeUO transporter, which is not functional in E. coli K-12 due to a frameshift mutation disrupting efeU. Similar to YfeX, the EfeB protein, although it is normally transported to the periplasm, is able to catalyze the cytoplasmic release of iron from hemin without destroying the tetrapyrrol ring [Letoffe09].
EfeB is a dimeric, non-covalently bound heme-containing peroxidase enzyme of the DyP-type peroxidase family, and is a substrate of the twin arginine translocation (Tat) system [Sturm06]. The Tat-system allows EfeB to assemble in the cytoplasm prior to transport [Sturm06]. The heme cofactor has been identified as FeIII-protoporphyrin IX [Sturm06].
EfeB may act to reduce Fe3+ to Fe2+ for transport or to oxidize Fe2+ during transport [Cao07a]. EfeB exhibits guaiacol peroxidase activity at an optimum pH of about 4.0 and may function under acid-stress conditions [Sturm06].
The crystal structure of EfeB has been determined in the apo form to a resolution of 2.0 Å; crystals with bound haem were obtained and diffract to 2.9 Å [Cartron07].
A yfeX efeB double mutant in a HasR-expressing strain is unable to use heme as an external source of iron [Letoffe09].
Locations: cytosol, periplasmic space, cytosol
|Map Position: [1,082,599 -> 1,083,870] (23.33 centisomes, 84°)||Length: 1272 bp / 423 aa|
Molecular Weight of Polypeptide: 46.754 kD (from nucleotide sequence), 45.1 kD (experimental) [Sturm06]
Molecular Weight of Multimer: 89.9 kD (experimental) [Sturm06]
Unification Links: ASAP:ABE-0003451, EchoBASE:EB1686, EcoGene:EG11735, EcoliWiki:b1019, OU-Microarray:b1019, PortEco:efeB, Pride:P31545, Protein Model Portal:P31545, RefSeq:NP_415538, RegulonDB:EG11735, SMR:P31545, String:511145.b1019, UniProt:P31545
Relationship Links: InterPro:IN-FAMILY:IPR006311, InterPro:IN-FAMILY:IPR006313, InterPro:IN-FAMILY:IPR006314, InterPro:IN-FAMILY:IPR011008, PDB:Structure:2Y4D, PDB:Structure:2Y4E, PDB:Structure:2Y4F, Pfam:IN-FAMILY:PF04261, Prosite:IN-FAMILY:PS51318, Prosite:IN-FAMILY:PS51404
In Paralogous Gene Group: 242 (2 members)
|MultiFun Terms:||transport → Accessory Factors Involved in Transport|
|Growth Medium||Growth?||T (°C)||O2||pH||Osm/L||Growth Observations|
|LB enriched||Yes||37||Aerobic||6.95||Yes [Gerdes03, Comment 1]|
|LB Lennox||Yes||37||Aerobic||7||Yes [Baba06, Comment 2]|
|M9 medium with 1% glycerol||Yes||37||Aerobic||7.2||0.35||Yes [Joyce06, Comment 3]|
|MOPS medium with 0.4% glucose||Yes||37||Aerobic||7.2||0.22||Yes [Baba06, Comment 2]|
Enzymatic reaction of: deferrochelatase (EfeB dimer)
EC Number: 22.214.171.124ferroheme b + 2 H+ → Fe2+ + protoporphyrin IX
The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction of enzyme catalysis.
The reaction is physiologically favored in the direction shown.
Subunit of: EfeU/EfeO/EfeB ferrous iron transporter; cryptic
Subunit composition of
EfeU/EfeO/EfeB ferrous iron transporter; cryptic = [EfeU_1][EfeO][EfeB]
hypothetical protein of the OFeT transport family = EfeU_1 (summary available)
conserved periplasmic protein = EfeO (summary available)
heme-containing peroxidase/deferrochelatase = EfeB (extended summary available)
EfeUOB is a cryptic Fe2+ transporter responsible for uptake of ferrous iron under conditions of iron limitation and low pH. All three components are required for efficient Fe2+ transport when EfeUOB is activated.
The functional efeU (ycdN) gene in E. coli Nissle 1917 encodes the oxidase-dependent, OFeT family ferrous iron permease, EfeU, which is an integral inner membrane protein with seven transmembrane segments [Grosse06]. efeU in E. coli K-12 has been disrupted by a frameshift mutation leaving the efeU_1 and efeU_2 fragments nonfunctional [Grosse06].
Deletion of efeU, efeO, or efeB did not result in any growth defects or other detectable phenotypes [Cao07a]. Expression of the corrected EfeU protein in a strain lacking all other known iron transporters resulted in improved growth and increased iron uptake [Cao07a, Grosse06]. Deletion of efeO or efeB caused a growth defect during iron limitation when corrected efeU is supplied [Cao07a].
efeUOB is induced at low pH due to phosphorylation of the CpxR component of the CpxAR two-component response regulator [Stancik02, Maurer05, Cao07a]. Expression of efeUOB increased in response to iron-depleted conditions in a Fe2+-Fur-dependent manner as well as to increased Cu2+ as excess Cu2+ impedes iron entry into the cell [Cao07a, Grosse06]. efeUOB is repressed by autoclaved stationary phase supernatant in DH5α [Ren04] and in an indirect response to expression of RhyB, which down-regulates iron-binding proteins and makes more Fe2+ available for Fur repression [Masse05]. Expression of EfeU decreased upon osmotic upshift [Weber02]. efeU_2 is also repressed under anaerobic conditions [Kang05]. efeB is repressed by luxS in W3110 [Wang05a]. Expression increased in response to FlhD/FlhC and Aer in MC1000 and YK410 strains [Pruss03].
|Signal-Sequence||1 -> 35|
|Chain||36 -> 423|
|Pfam PF04261||61 -> 410|
|Protein-Segment||236 -> 238|
|Protein-Segment||334 -> 336|
Peter D. Karp on Thu Jan 16, 2003:
Predicted gene function revised as a result of E. coli genome reannotation by Serres et al. [Serres01].
10/20/97 Gene b1019 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG11735; confirmed by SwissProt match.
Baba06: Baba T, Ara T, Hasegawa M, Takai Y, Okumura Y, Baba M, Datsenko KA, Tomita M, Wanner BL, Mori H (2006). "Construction of Escherichia coli K-12 in-frame, single-gene knockout mutants: the Keio collection." Mol Syst Biol 2;2006.0008. PMID: 16738554
Cao07a: Cao J, Woodhall MR, Alvarez J, Cartron ML, Andrews SC (2007). "EfeUOB (YcdNOB) is a tripartite, acid-induced and CpxAR-regulated, low-pH Fe2+ transporter that is cryptic in Escherichia coli K-12 but functional in E. coli O157:H7." Mol Microbiol 65(4);857-75. PMID: 17627767
Cartron07: Cartron ML, Mitchell SA, Woodhall MR, Andrews SC, Watson KA (2007). "Preliminary X-ray diffraction analysis of YcdB from Escherichia coli: a novel haem-containing and Tat-secreted periplasmic protein with a potential role in iron transport." Acta Crystallogr Sect F Struct Biol Cryst Commun 63(Pt 1);37-41. PMID: 17183171
Finn14: Finn RD, Bateman A, Clements J, Coggill P, Eberhardt RY, Eddy SR, Heger A, Hetherington K, Holm L, Mistry J, Sonnhammer EL, Tate J, Punta M (2014). "Pfam: the protein families database." Nucleic Acids Res 42(Database issue);D222-30. PMID: 24288371
Gerdes03: Gerdes SY, Scholle MD, Campbell JW, Balazsi G, Ravasz E, Daugherty MD, Somera AL, Kyrpides NC, Anderson I, Gelfand MS, Bhattacharya A, Kapatral V, D'Souza M, Baev MV, Grechkin Y, Mseeh F, Fonstein MY, Overbeek R, Barabasi AL, Oltvai ZN, Osterman AL (2003). "Experimental determination and system level analysis of essential genes in Escherichia coli MG1655." J Bacteriol 185(19);5673-84. PMID: 13129938
Graubner07: Graubner W, Schierhorn A, Bruser T (2007). "DnaK plays a pivotal role in Tat targeting of CueO and functions beside SlyD as a general Tat signal binding chaperone." J Biol Chem 282(10);7116-24. PMID: 17215254
Joyce06: Joyce AR, Reed JL, White A, Edwards R, Osterman A, Baba T, Mori H, Lesely SA, Palsson BO, Agarwalla S (2006). "Experimental and computational assessment of conditionally essential genes in Escherichia coli." J Bacteriol 188(23);8259-71. PMID: 17012394
Kang05: Kang Y, Weber KD, Qiu Y, Kiley PJ, Blattner FR (2005). "Genome-wide expression analysis indicates that FNR of Escherichia coli K-12 regulates a large number of genes of unknown function." J Bacteriol 187(3);1135-60. PMID: 15659690
Letoffe09: Letoffe S, Heuck G, Delepelaire P, Lange N, Wandersman C (2009). "Bacteria capture iron from heme by keeping tetrapyrrol skeleton intact." Proc Natl Acad Sci U S A 106(28):11719-24. PMID: 19564607
Maurer05: Maurer LM, Yohannes E, Bondurant SS, Radmacher M, Slonczewski JL (2005). "pH regulates genes for flagellar motility, catabolism, and oxidative stress in Escherichia coli K-12." J Bacteriol 187(1);304-19. PMID: 15601715
Pruss03: Pruss BM, Campbell JW, Van Dyk TK, Zhu C, Kogan Y, Matsumura P (2003). "FlhD/FlhC is a regulator of anaerobic respiration and the Entner-Doudoroff pathway through induction of the methyl-accepting chemotaxis protein Aer." J Bacteriol 185(2);534-43. PMID: 12511500
Ren04: Ren D, Bedzyk LA, Ye RW, Thomas SM, Wood TK (2004). "Stationary-phase quorum-sensing signals affect autoinducer-2 and gene expression in Escherichia coli." Appl Environ Microbiol 70(4);2038-43. PMID: 15066794
Stancik02: Stancik LM, Stancik DM, Schmidt B, Barnhart DM, Yoncheva YN, Slonczewski JL (2002). "pH-dependent expression of periplasmic proteins and amino acid catabolism in Escherichia coli." J Bacteriol 184(15);4246-58. PMID: 12107143
Sturm06: Sturm A, Schierhorn A, Lindenstrauss U, Lilie H, Bruser T (2006). "YcdB from Escherichia coli reveals a novel class of Tat-dependently translocated hemoproteins." J Biol Chem 281(20);13972-8. PMID: 16551627
Wang05a: Wang L, Li J, March JC, Valdes JJ, Bentley WE (2005). "luxS-dependent gene regulation in Escherichia coli K-12 revealed by genomic expression profiling." J Bacteriol 187(24);8350-60. PMID: 16321939
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