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Infection and Immunity, November 2009, p. 4934-4939, Vol. 77, No. 11
0019-9567/09/$08.00+0     doi:10.1128/IAI.00714-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

A Periplasmic Thioredoxin-Like Protein Plays a Role in Defense against Oxidative Stress in Neisseria gonorrhoeae{triangledown}

Maud E. S. Achard,1 Amanda J. Hamilton,1 Tarek Dankowski,1 Begoña Heras,2 Mark S. Schembri,1 Jennifer L. Edwards,3 Michael P. Jennings,1,{dagger} and Alastair G. McEwan1*

School of Chemistry and Molecular Biosciences,1 Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia,2 Centre for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio 432053

Received 25 June 2009/ Returned for modification 9 July 2009/ Accepted 11 August 2009

Thioredoxin-like proteins of the TlpA/ResE/CcmG subfamily are known to face the periplasm in gram-negative bacteria. Using the tlpA gene of Bradyrhizobium japonicum as a query, we identified a locus (NGO1923) in Neisseria gonorrhoeae that encodes a thioredoxin-like protein (NG_TlpA). Bioinformatics analysis indicated that the predicted NG_TlpA protein contained a cleavable signal peptide at the N terminus, and secondary structure analysis identified a thioredoxin fold with a helical insertion (~25 residues), similar to that found in B. japonicum TlpA but absent in cytoplasmic thioredoxins. Biochemical characterization of a recombinant form of NG_TlpA revealed a standard redox potential (E0') of –206 mV. This property and the observation that the oxidized form of the protein exhibited greater thermal stability than the reduced species indicated that NG_TlpA is a reducing thioredoxin and not an oxidizing thiol-disulfide oxidoreductase like DsbA. The thioredoxin activity of NG_TlpA was confirmed in an insulin disulfide reduction assay. A tlpA mutant of N. gonorrhoeae strain 1291 was found to be highly sensitive to oxidative killing by paraquat and hydrogen peroxide, indicating an antioxidant role for the NG_TlpA in this bacterium. The tlpA mutant also exhibited reduced intracellular survival in human primary cervical epithelial cells.

* Corresponding author. Mailing address: School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane 4072, Australia. Phone: 61 7 3365 4622. Fax: 61 7 3365 4273. E-mail: mcewan{at}uq.edu.au

{triangledown} Published ahead of print on 17 August 2009.

Editor: J. N. Weiser

{dagger} Present address: Institute for Glycomics, Griffith University, Gold Coast 4222, Australia.

Infection and Immunity, November 2009, p. 4934-4939, Vol. 77, No. 11
0019-9567/09/$08.00+0     doi:10.1128/IAI.00714-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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