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 Newton, G. L. Articles by Fahey, R. C. Search for Related Content PubMed PubMed Citation Articles by Newton, G. L. Articles by Fahey, R. C.

 Previous Article  |  Next Article 

Journal of Bacteriology, November 2005, p. 7309-7316, Vol. 187, No. 21
0021-9193/05/$08.00+0     doi:10.1128/JB.187.21.7309-7316.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

A Mycothiol Synthase Mutant of Mycobacterium smegmatis Produces Novel Thiols and Has an Altered Thiol Redox Status

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California

Received 8 June 2005/ Accepted 8 August 2005

Mycobacteria and other actinomycetes do not produce glutathione but make mycothiol (MSH; AcCys-GlcN-Ins) that has functions similar to those of glutathione and is essential for growth of Mycobacterium tuberculosis. Mycothiol synthase (MshD) catalyzes N acetylation of Cys-GlcN-Ins to produce MSH in Mycobacterium smegmatis mc²155, and Cys-GlcN-Ins is maintained at a low level. The mycothiol synthase mutant, the mshD::Tn5 mutant, produces high levels of Cys-GlcN-Ins along with two novel thiols, N-formyl-Cys-GlcN-Ins and N-succinyl-Cys-GlcN-Ins, and a small amount of MSH. The nonenzymatic reaction of acyl-coenzyme A (CoA) with Cys-GlcN-Ins to produce acyl-Cys-GlcN-Ins is a facile reaction under physiologic conditions, with succinyl-CoA being an order of magnitude more reactive than acetyl-CoA. The uncatalyzed reaction rates are adequate to account for the observed production of N-succinyl-Cys-GlcN-Ins and MSH under physiologic conditions. It was shown that the N-acyl-Cys-GlcN-Ins compounds are maintained in a substantially reduced state in the mutant but that Cys-GlcN-Ins exists in disulfide forms at 5 to 40% at different stages of growth. MSH was able to facilitate reduction of N-succinyl-Cys-GlcN-Ins disulfide through thiol-disulfide exchange, but N-formyl-Cys-GlcN-Ins was ineffective. The oxidized state of Cys-GlcN-Ins in cells appears to result from a high susceptibility to autoxidation and a low capacity of the cell to reduce its disulfide forms. The mutant exhibited no enhanced sensitivity to hydrogen peroxide, tert-butyl hydroperoxide, or cumene hydroperoxide relative to the parent strain, suggesting that the most abundant thiol, N-formyl-Cys-GlcN-Ins, functions as a substitute for MSH.

This article has been cited by other articles:

• Newton, G. L., Buchmeier, N., Fahey, R. C. (2008). Biosynthesis and Functions of Mycothiol, the Unique Protective Thiol of Actinobacteria. Microbiol. Mol. Biol. Rev. 72: 471-494 [Abstract] [Full Text]  
• Vetting, M. W., Frantom, P. A., Blanchard, J. S. (2008). Structural and Enzymatic Analysis of MshA from Corynebacterium glutamicum: SUBSTRATE-ASSISTED CATALYSIS. J. Biol. Chem. 283: 15834-15844 [Abstract] [Full Text]  
• Bzymek, K. P., Newton, G. L., Ta, P., Fahey, R. C. (2007). Mycothiol Import by Mycobacterium smegmatis and Function as a Resource for Metabolic Precursors and Energy Production. J. Bacteriol. 189: 6796-6805 [Abstract] [Full Text]  
• Garg, S., Vitvitsky, V., Gendelman, H. E., Banerjee, R. (2006). Monocyte Differentiation, Activation, and Mycobacterial Killing Are Linked to Transsulfuration-dependent Redox Metabolism. J. Biol. Chem. 281: 38712-38720 [Abstract] [Full Text]  
• Newton, G. L., Ta, P., Bzymek, K. P., Fahey, R. C. (2006). Biochemistry of the Initial Steps of Mycothiol Biosynthesis. J. Biol. Chem. 281: 33910-33920 [Abstract] [Full Text]  
• Buchmeier, N. A., Newton, G. L., Fahey, R. C. (2006). A Mycothiol Synthase Mutant of Mycobacterium tuberculosis Has an Altered Thiol-Disulfide Content and Limited Tolerance to Stress.. J. Bacteriol. 188: 6245-6252 [Abstract] [Full Text]  
• Feng, J., Che, Y., Milse, J., Yin, Y.-J., Liu, L., Ruckert, C., Shen, X.-H., Qi, S.-W., Kalinowski, J., Liu, S.-J. (2006). The Gene ncgl2918 Encodes a Novel Maleylpyruvate Isomerase That Needs Mycothiol as Cofactor and Links Mycothiol Biosynthesis and Gentisate Assimilation in Corynebacterium glutamicum. J. Biol. Chem. 281: 10778-10785 [Abstract] [Full Text]