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The cobalamin (coenzyme B12) biosynthetic genes of Escherichia coli.
J Bacteriol. 1995 Nov; 177(22):6371-80.JB

Abstract

The enteric bacterium Escherichia coli synthesizes cobalamin (coenzyme B12) only when provided with the complex intermediate cobinamide. Three cobalamin biosynthetic genes have been cloned from Escherichia coli K-12, and their nucleotide sequences have been determined. The three genes form an operon (cob) under the control of several promoters and are induced by cobinamide, a precursor of cobalamin. The cob operon of E. coli comprises the cobU gene, encoding the bifunctional cobinamide kinase-guanylyltransferase; the cobS gene, encoding cobalamin synthetase; and the cobT gene, encoding dimethylbenzimidazole phosphoribosyltransferase. The physiological roles of these sequences were verified by the isolation of Tn10 insertion mutations in the cobS and cobT genes. All genes were named after their Salmonella typhimurium homologs and are located at the corresponding positions on the E. coli genetic map. Although the nucleotide sequences of the Salmonella cob genes and the E. coli cob genes are homologous, they are too divergent to have been derived from an operon present in their most recent common ancestor. On the basis of comparisons of G+C content, codon usage bias, dinucleotide frequencies, and patterns of synonymous and nonsynonymous substitutions, we conclude that the cob operon was introduced into the Salmonella genome from an exogenous source. The cob operon of E. coli may be related to cobalamin synthetic genes now found among non-Salmonella enteric bacteria.

Authors+Show Affiliations

Department of Biology, University of Utah, Salt Lake City 84112, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

7592411

Citation

Lawrence, J G., and J R. Roth. "The Cobalamin (coenzyme B12) Biosynthetic Genes of Escherichia Coli." Journal of Bacteriology, vol. 177, no. 22, 1995, pp. 6371-80.
Lawrence JG, Roth JR. The cobalamin (coenzyme B12) biosynthetic genes of Escherichia coli. J Bacteriol. 1995;177(22):6371-80.
Lawrence, J. G., & Roth, J. R. (1995). The cobalamin (coenzyme B12) biosynthetic genes of Escherichia coli. Journal of Bacteriology, 177(22), 6371-80.
Lawrence JG, Roth JR. The Cobalamin (coenzyme B12) Biosynthetic Genes of Escherichia Coli. J Bacteriol. 1995;177(22):6371-80. PubMed PMID: 7592411.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The cobalamin (coenzyme B12) biosynthetic genes of Escherichia coli. AU - Lawrence,J G, AU - Roth,J R, PY - 1995/11/1/pubmed PY - 1995/11/1/medline PY - 1995/11/1/entrez SP - 6371 EP - 80 JF - Journal of bacteriology JO - J Bacteriol VL - 177 IS - 22 N2 - The enteric bacterium Escherichia coli synthesizes cobalamin (coenzyme B12) only when provided with the complex intermediate cobinamide. Three cobalamin biosynthetic genes have been cloned from Escherichia coli K-12, and their nucleotide sequences have been determined. The three genes form an operon (cob) under the control of several promoters and are induced by cobinamide, a precursor of cobalamin. The cob operon of E. coli comprises the cobU gene, encoding the bifunctional cobinamide kinase-guanylyltransferase; the cobS gene, encoding cobalamin synthetase; and the cobT gene, encoding dimethylbenzimidazole phosphoribosyltransferase. The physiological roles of these sequences were verified by the isolation of Tn10 insertion mutations in the cobS and cobT genes. All genes were named after their Salmonella typhimurium homologs and are located at the corresponding positions on the E. coli genetic map. Although the nucleotide sequences of the Salmonella cob genes and the E. coli cob genes are homologous, they are too divergent to have been derived from an operon present in their most recent common ancestor. On the basis of comparisons of G+C content, codon usage bias, dinucleotide frequencies, and patterns of synonymous and nonsynonymous substitutions, we conclude that the cob operon was introduced into the Salmonella genome from an exogenous source. The cob operon of E. coli may be related to cobalamin synthetic genes now found among non-Salmonella enteric bacteria. SN - 0021-9193 UR - https://www.unboundmedicine.com/medline/citation/7592411/The_cobalamin__coenzyme_B12__biosynthetic_genes_of_Escherichia_coli_ L2 - http://jb.asm.org/cgi/pmidlookup?view=long&pmid=7592411 DB - PRIME DP - Unbound Medicine ER -