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 Elton, T. C. Articles by Hazes, B. Search for Related Content PubMed PubMed Citation Articles by Elton, T. C. Articles by Hazes, B.

 Previous Article  |  Next Article 

Journal of Bacteriology, December 2005, p. 8267-8277, Vol. 187, No. 24
0021-9193/05/$08.00+0     doi:10.1128/JB.187.24.8267-8277.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

F-Like Type IV Secretion Systems Encode Proteins with Thioredoxin Folds That Are Putative DsbC Homologues

Trevor C. Elton,¹ Samantha J. Holland,¹ Laura S. Frost,^1* and Bart Hazes²

Departments of Biological Sciences,¹ Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada T6G 2E9²

Received 14 April 2005/ Accepted 3 October 2005

F and R27 are conjugative plasmids of enteric bacteria belonging to the IncF and IncHI1 plasmid incompatibility groups, respectively. Based on sequence analysis, two genes of the F transfer region, traF and trbB, and three genes of the R27 transfer region, trhF, dsbC, and htdT, are predicted to encode periplasmic proteins containing a C-terminal thioredoxin fold. The C-X-X-C active-site motif of thioredoxins is present in all of these proteins except TraF_F. Escherichia coli carrying a dsbA mutation, which is deficient in disulfide bond formation, cannot synthesize pili and exhibits hypersensitivity to dithiothreitol (DTT) as monitored by mating ability. Overproduction of the E. coli disulfide bond isomerase DsbC, TrbB_F, DsbC_R27, or HtdT_R27, but not TraF_F or TrhF_R27, reverses this hypersensitivity to DTT. Site-directed mutagenesis established that the C-X-X-C motif was necessary for this activity. Secretion into the periplasm of the C-terminal regions of TrbB_F and DsbC_R27, containing putative thioredoxin folds, but not TrhF_R27, partially complemented the host dsbA mutation. A trbB_F deletion mutant showed a 10-fold-lower mating efficiency in an E. coli dsbC null strain but had no phenotype in wild-type E. coli, suggesting redundancy in function between TrbB_F and E. coli DsbC. Our results indicate that TrbB_F, DsbC_R27, and HtdT_R27 are putative disulfide bond isomerases for their respective transfer systems. TraF_F is essential for conjugation but appears to have a function other than disulfide bond chemistry.

---

* Corresponding author. Mailing address: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9. Phone: (780) 492-0672. Fax: (780) 492-9234. E-mail: laura.frost{at}ualberta.ca.

---

Journal of Bacteriology, December 2005, p. 8267-8277, Vol. 187, No. 24
0021-9193/05/$08.00+0     doi:10.1128/JB.187.24.8267-8277.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Masip, L., Klein-Marcuschamer, D., Quan, S., Bardwell, J. C. A., Georgiou, G. (2008). Laboratory Evolution of Escherichia coli Thioredoxin for Enhanced Catalysis of Protein Oxidation in the Periplasm Reveals a Phylogenetically Conserved Substrate Specificity Determinant. J. Biol. Chem. 283: 840-848 [Abstract] [Full Text]  
• Schneider, S., Schneidereit, A., Udvardi, P., Hammes, U., Gramann, M., Dietrich, P., Sauer, N. (2007). Arabidopsis INOSITOL TRANSPORTER2 Mediates H+ Symport of Different Inositol Epimers and Derivatives across the Plasma Membrane. Plant Physiol. 145: 1395-1407 [Abstract] [Full Text]