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Journal of Bacteriology, November 2008, p. 7087-7095, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00159-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Functional Studies of Multiple Thioredoxins from Mycobacterium tuberculosis{triangledown} ,{dagger}

Mohd Akif,1 Garima Khare,2 Anil K. Tyagi,2 Shekhar C. Mande,1* and Abhijit A. Sardesai3*

Laboratory of Structural Biology,1 Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500076, India,3 Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India2

Received 31 January 2008/ Accepted 13 August 2008

Cytoplasmic protein reduction via generalized thiol/disulfide exchange reactions and maintenance of cellular redox homeostasis is mediated by the thioredoxin superfamily of proteins. Here, we describe the characterization of the thioredoxin system from Mycobacterium tuberculosis, whose genome bears the potential to encode three putative thioredoxins from the open reading frames designated trxAMtb, trxBMtb, and trxCMtb. We show that all three thioredoxins, overproduced in Escherichia coli, are able to reduce insulin, a model substrate, in the presence of dithiothreitol. However, we observe that thioredoxin reductase is not capable of reducing TrxAMtb in an NADPH-dependent manner, indicating that only TrxBMtb and TrxCMtb are the biologically active disulfide reductases. The absence of detectable mRNA transcripts of trxAMtb observed when M. tuberculosis strain H37Rv was cultivated under different growth conditions suggests that trxAMtb expression may be cryptic. The measured redox potentials of TrxBMtb and TrxCMtb (–262 ± 2 mV and –269 ± 2 mV, respectively) render these proteins somewhat more oxidizing than E. coli thioredoxin 1 (TrxA). In E. coli strains lacking components of cytoplasmic protein reduction pathways, heterologous expression of the mycobacterial thioredoxins was able to effectively substitute for their function.

* Corresponding author. Mailing address for Shekhar C. Mande: Laboratory of Structural Biology, Centre for DNA Fingerprinting and Diagnostics, Nacharam, Hyderabad 500076, India. Phone: 91-40-27171442. Fax: 91-40-27155610. E-mail: shekhar{at}cdfd.org.in. Mailing address for Abhijit A. Sardesai: Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Nacharam, Hyderabad 500076, India. Phone: 91-40-27171442. Fax: 91-40-27155610. E-mail: abhijit{at}cdfd.org.in

{triangledown} Published ahead of print on 22 August 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, November 2008, p. 7087-7095, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00159-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Basu, D., Khare, G., Singh, S., Tyagi, A., Khosla, S., Mande, S. C. (2009). A novel nucleoid-associated protein of Mycobacterium tuberculosis is a sequence homolog of GroEL. Nucleic Acids Res 37: 4944-4954 [Abstract] [Full Text]  


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