Functional and bioinformatics analysis of two Campylobacter jejuni homologs of the thiol-disulfide oxidoreductase, DsbA

PLoS One. 2014 Sep 2;9(9):e106247. doi: 10.1371/journal.pone.0106247. eCollection 2014.

Abstract

Background: Bacterial Dsb enzymes are involved in the oxidative folding of many proteins, through the formation of disulfide bonds between their cysteine residues. The Dsb protein network has been well characterized in cells of the model microorganism Escherichia coli. To gain insight into the functioning of the Dsb system in epsilon-Proteobacteria, where it plays an important role in the colonization process, we studied two homologs of the main Escherichia coli Dsb oxidase (EcDsbA) that are present in the cells of the enteric pathogen Campylobacter jejuni, the most frequently reported bacterial cause of human enteritis in the world.

Methods and results: Phylogenetic analysis suggests the horizontal transfer of the epsilon-Proteobacterial DsbAs from a common ancestor to gamma-Proteobacteria, which then gave rise to the DsbL lineage. Phenotype and enzymatic assays suggest that the two C. jejuni DsbAs play different roles in bacterial cells and have divergent substrate spectra. CjDsbA1 is essential for the motility and autoagglutination phenotypes, while CjDsbA2 has no impact on those processes. CjDsbA1 plays a critical role in the oxidative folding that ensures the activity of alkaline phosphatase CjPhoX, whereas CjDsbA2 is crucial for the activity of arylsulfotransferase CjAstA, encoded within the dsbA2-dsbB-astA operon.

Conclusions: Our results show that CjDsbA1 is the primary thiol-oxidoreductase affecting life processes associated with bacterial spread and host colonization, as well as ensuring the oxidative folding of particular protein substrates. In contrast, CjDsbA2 activity does not affect the same processes and so far its oxidative folding activity has been demonstrated for one substrate, arylsulfotransferase CjAstA. The results suggest the cooperation between CjDsbA2 and CjDsbB. In the case of the CjDsbA1, this cooperation is not exclusive and there is probably another protein to be identified in C. jejuni cells that acts to re-oxidize CjDsbA1. Altogether the data presented here constitute the considerable insight to the Epsilonproteobacterial Dsb systems, which have been poorly understood so far.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agglutination
  • Alkaline Phosphatase / metabolism
  • Arylsulfotransferase / metabolism
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Campylobacter jejuni / enzymology
  • Computational Biology / methods*
  • Escherichia coli / metabolism
  • Genetic Complementation Test
  • Humans
  • Insulin / metabolism
  • Models, Molecular
  • Movement
  • Mutation / genetics
  • Oxidation-Reduction
  • Phylogeny
  • Protein Aggregates
  • Protein Binding
  • Protein Disulfide Reductase (Glutathione) / chemistry
  • Protein Disulfide Reductase (Glutathione) / metabolism*
  • Protein Folding
  • Sequence Homology, Amino Acid*

Substances

  • Bacterial Proteins
  • Insulin
  • Protein Aggregates
  • Protein Disulfide Reductase (Glutathione)
  • Arylsulfotransferase
  • Alkaline Phosphatase

Grants and funding

This work was funded by the grant of Polish Ministry of Science and Higher Education (grant No. N401 183 31/3968 and N N303 550 439). EW has been supported by the Polish Ministry of Science and Higher Education (grant POIG.02.03.00-00-003/09). SDH has been supported by the National Science Centre (NCN, grant 2011/03/D/NZ8/03011) and by the Polish Ministry of Science and Higher Education (MNiSW, fellowship for outstanding young scientists). JMB has been supported by the 7th Framework Programme of the EU (grant HEALTHPROT, contract number 229676) and by the statutory funds of IIMCB. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.