This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tuite, N. L. Articles by O'Byrne, C. P. Search for Related Content PubMed PubMed Citation Articles by Tuite, N. L. Articles by O'Byrne, C. P.

 Previous Article  |  Next Article 

Journal of Bacteriology, July 2005, p. 4362-4371, Vol. 187, No. 13
0021-9193/05/$08.00+0     doi:10.1128/JB.187.13.4362-4371.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Homocysteine Toxicity in Escherichia coli Is Caused by a Perturbation of Branched-Chain Amino Acid Biosynthesis

Department of Microbiology, National University of Ireland-Galway, Galway, Ireland

Received 10 March 2005/ Accepted 11 March 2005

In Escherichia coli the sulfur-containing amino acid homocysteine (Hcy) is the last intermediate on the methionine biosynthetic pathway. Supplementation of a glucose-based minimal medium with Hcy at concentrations greater than 0.2 mM causes the growth of E. coli Frag1 to be inhibited. Supplementation of Hcy-treated cultures with combinations of branched-chain amino acids containing isoleucine or with isoleucine alone reversed the inhibitory effects of Hcy on growth. The last intermediate of the isoleucine biosynthetic pathway, -keto-ß-methylvalerate, could also alleviate the growth inhibition caused by Hcy. Analysis of amino acid pools in Hcy-treated cells revealed that alanine, valine, and glutamate levels are depleted. Isoleucine could reverse the effects of Hcy on the cytoplasmic pools of valine and alanine. Supplementation of the culture medium with alanine gave partial relief from the inhibitory effects of Hcy. Enzyme assays revealed that the first step of the isoleucine biosynthetic pathway, catalyzed by threonine deaminase, was sensitive to inhibition by Hcy. The gene encoding threonine deaminase, ilvA, was found to be transcribed at higher levels in the presence of Hcy. Overexpression of the ilvA gene from a plasmid could overcome Hcy-mediated growth inhibition. Together, these data indicate that in E. coli Hcy toxicity is caused by a perturbation of branched-chain amino acid biosynthesis that is caused, at least in part, by the inhibition of threonine deaminase.

This article has been cited by other articles:

• Valle, J., Da Re, S., Schmid, S., Skurnik, D., D'Ari, R., Ghigo, J.-M. (2008). The Amino Acid Valine Is Secreted in Continuous-Flow Bacterial Biofilms. J. Bacteriol. 190: 264-274 [Abstract] [Full Text]  
• Chwatko, G., Boers, G. H. J., Strauss, K. A., Shih, D. M., Jakubowski, H. (2007). Mutations in methylenetetrahydrofolate reductase or cystathionine {beta}-syntase gene, or a high-methionine diet, increase homocysteine thiolactone levels in humans and mice. FASEB J. 21: 1707-1713 [Abstract] [Full Text]  
• Coleman, S. A., Fischer, E. R., Cockrell, D. C., Voth, D. E., Howe, D., Mead, D. J., Samuel, J. E., Heinzen, R. A. (2007). Proteome and Antigen Profiling of Coxiella burnetii Developmental Forms. Infect. Immun. 75: 290-298 [Abstract] [Full Text]  
• Zimny, J., Sikora, M., Guranowski, A., Jakubowski, H. (2006). Protective Mechanisms against Homocysteine Toxicity: THE ROLE OF BLEOMYCIN HYDROLASE. J. Biol. Chem. 281: 22485-22492 [Abstract] [Full Text]  
• Walters, M., Sircili, M. P., Sperandio, V. (2006). AI-3 Synthesis Is Not Dependent on luxS in Escherichia coli.. J. Bacteriol. 188: 5668-5681 [Abstract] [Full Text]  
• Fraser, K. R., Tuite, N. L., Bhagwat, A., O'Byrne, C. P. (2006). Global effects of homocysteine on transcription in Escherichia coli: induction of the gene for the major cold-shock protein, CspA.. Microbiology 152: 2221-2231 [Abstract] [Full Text]