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Gene Review

btuB  -  vitamin B12/cobalamin outer membrane...

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK3958, JW3938, bfe, cer, dcrC
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Disease relevance of btuB

  • The btuB product is the outer membrane receptor for cobalamins, bacteriophage BF23, and the E colicins [1].
  • We report that the 5'-untranslated sequence of the Escherichia coli btuB mRNA assumes a more proactive role in metabolic monitoring and genetic control [2].
  • Strains of Salmonella typhimurium with mutations in the cobalamin synthesis pathway (Cob) and in btuB were used in a mouse model of virulence [3].
  • The argR gene of Bacillus subtilis complements an E.coli argR deficiency for cer-mediated recombination despite the two proteins having only 27% amino acid identity [4].
  • Thermoinduction of cells of E. coli carrying prophage lambdacI857 within the bfe gene brings about not only "escape synthesis" of core subunits of the DNA-dependent RNA polymerase (RNA nucleotidyltransferase, nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2-7-7-6), but also a striking stimulation of sigma factor synthesis [5].

High impact information on btuB

  • We demonstrate that Xer recombination at plasmid dif sites occurs efficiently only when FtsK is present and under conditions that allow chromosomal dimer formation, whereas recombination at the plasmid sites cer and psi is independent of these factors [6].
  • The argR protein binds to cer DNA both in vivo and in vitro in the presence of arginine [4].
  • Two of the C-terminal btuB mutations are located within the region of overlap with the recently identified dga (murl) gene [7].
  • Sixteen signal peptides were found, including those of lamB, btuB, and malE [8].
  • Mutational analysis showed that the btuB start codon and a hairpin structure that can sequester the Shine-Dalgarno sequence are necessary for cobalamin-dependent regulation and that translation of the TRR is necessary for extended RNA stability and for expression of the transcriptional fusion [9].

Biological context of btuB

  • The nucleotide sequence of a 2220-base-pair fragment containing the btuB gene of Escherichia coli was determined [10].
  • These results indicate that the primary control of btuB expression by cobalamin occurs at the level of translation initiation, which directly affects the level and stability of btuB RNA in a process that requires the presence of the intact translated regulatory region [9].
  • Mutations in tonB that suppressed the transport defect phenotype of these btuB mutations were isolated [11].
  • The Escherichia coli btuB product is an outer membrane protein that mediates the TonB-coupled active transport of cobalamins and the uptake of the E colicins and bacteriophage BF23 [12].
  • The extensive sequence conservation within the first 300 transcribed nucleotides, which include the leader and early part of the coding sequence, supports the proposed role of this region in the regulation of btuB gene expression [13].

Anatomical context of btuB


Associations of btuB with chemical compounds

  • The btuE mutations did not impair adenosyl-cobalamin dependent catabolism of ethanolamine or repression of btuB expression [15].
  • An effect of the context of the remainder of the protein was seen, since the same substitution (valine 10----glycine) in btuB and cir responded differently to the suppressors [11].

Other interactions of btuB

  • The trmA and the btuB (encoding the vitamin B12 outer membrane receptor protein) promoters are divergent promoters separated by 102 bp between the transcriptional start sites [16].
  • Altered cobalamin metabolism in Escherichia coli btuR mutants affects btuB gene regulation [17].
  • The various tonB mutations differed markedly in their suppression activities on different btuB or cir mutations [11].


  1. Point mutations in a conserved region (TonB box) of Escherichia coli outer membrane protein BtuB affect vitamin B12 transport. Gudmundsdottir, A., Bell, P.E., Lundrigan, M.D., Bradbeer, C., Kadner, R.J. J. Bacteriol. (1989) [Pubmed]
  2. Genetic control by a metabolite binding mRNA. Nahvi, A., Sudarsan, N., Ebert, M.S., Zou, X., Brown, K.L., Breaker, R.R. Chem. Biol. (2002) [Pubmed]
  3. Elimination of the vitamin B12 uptake or synthesis pathway does not diminish the virulence of Escherichia coli K1 or Salmonella typhimurium in three model systems. Sampson, B.A., Gotschlich, E.C. Infect. Immun. (1992) [Pubmed]
  4. The arginine repressor is essential for plasmid-stabilizing site-specific recombination at the ColE1 cer locus. Stirling, C.J., Szatmari, G., Stewart, G., Smith, M.C., Sherratt, D.J. EMBO J. (1988) [Pubmed]
  5. Induction of sigma factor synthesis in Escherichia coli by the N gene product of bacteriophage lambda. Nakamura, Y., Yura, T. Proc. Natl. Acad. Sci. U.S.A. (1976) [Pubmed]
  6. FtsK-dependent and -independent pathways of Xer site-specific recombination. Recchia, G.D., Aroyo, M., Wolf, D., Blakely, G., Sherratt, D.J. EMBO J. (1999) [Pubmed]
  7. Structure-function analysis of the vitamin B12 receptor of Escherichia coli by means of informational suppression. Hufton, S.E., Ward, R.J., Bunce, N.A., Armstrong, J.T., Fletcher, A.J., Glass, R.E. Mol. Microbiol. (1995) [Pubmed]
  8. Analysis of the Escherichia coli genome. IV. DNA sequence of the region from 89.2 to 92.8 minutes. Blattner, F.R., Burland, V., Plunkett, G., Sofia, H.J., Daniels, D.L. Nucleic Acids Res. (1993) [Pubmed]
  9. Coupled changes in translation and transcription during cobalamin-dependent regulation of btuB expression in Escherichia coli. Nou, X., Kadner, R.J. J. Bacteriol. (1998) [Pubmed]
  10. Nucleotide sequence of the gene for the vitamin B12 receptor protein in the outer membrane of Escherichia coli. Heller, K., Kadner, R.J. J. Bacteriol. (1985) [Pubmed]
  11. Genetic suppression demonstrates interaction of TonB protein with outer membrane transport proteins in Escherichia coli. Bell, P.E., Nau, C.D., Brown, J.T., Konisky, J., Kadner, R.J. J. Bacteriol. (1990) [Pubmed]
  12. Deletions or duplications in the BtuB protein affect its level in the outer membrane of Escherichia coli. Köster, W., Gudmundsdottir, A., Lundrigan, M.D., Seiffert, A., Kadner, R.J. J. Bacteriol. (1991) [Pubmed]
  13. Conserved structural and regulatory regions in the Salmonella typhimurium btuB gene for the outer membrane vitamin B12 transport protein. Wei, B.Y., Bradbeer, C., Kadner, R.J. Res. Microbiol. (1992) [Pubmed]
  14. Interdependence of calcium and cobalamin binding by wild-type and mutant BtuB protein in the outer membrane of Escherichia coli. Bradbeer, C., Gudmundsdottir, A. J. Bacteriol. (1990) [Pubmed]
  15. Vitamin B12 transport in Escherichia coli K12 does not require the btuE gene of the btuCED operon. Rioux, C.R., Kadner, R.J. Mol. Gen. Genet. (1989) [Pubmed]
  16. The trmA promoter has regulatory features and sequence elements in common with the rRNA P1 promoter family of Escherichia coli. Gustafsson, C., Lindström, P.H., Hagervall, T.G., Esberg, K.B., Björk, G.R. J. Bacteriol. (1991) [Pubmed]
  17. Altered cobalamin metabolism in Escherichia coli btuR mutants affects btuB gene regulation. Lundrigan, M.D., Kadner, R.J. J. Bacteriol. (1989) [Pubmed]
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