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Author Notes:

Corresponding Author: Adriano O. Henriques Email: aoh@itqb.unl.pt

Conceived and designed the experiments: AOH CPM.

Performed the experiments: LC FV MS CMG.

Analyzed the data: LC FV MS CMG CPM AOH.

Wrote the paper: LC FV AOH.

We thank D. Rudner (Harvard Medical School) for the gift of strains.

Competing Interests: Dr. Cláudio Gomes, a co-author of the manuscript, is a PLOS ONE Editorial Board member.

This does not alter the authors' adherence to PLOS ONE Editorial policies and criteria.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.


Research Funding:

This work was supported by grants POCTI/BIA-BCM/60855/2004 and PEst-OE/EQB/LA0004/2011 from “Fundação para a Ciência e a Tecnologia” (FCT) to A.O.H., and by National Institute of General and Medical Sciences Public Health Services R01 Grant GM54395-29 to C.P.M. LC (SFRH/BD/6489/2001) and M.S (SFRH/BPD/36328/2007) and F.V. (SFRH/BPD/26470/2006) were the recipients of a PhD (LC) and post doctoral fellowships (MS and FV) from the FCT.


  • Science & Technology
  • Multidisciplinary Sciences
  • Science & Technology - Other Topics
  • YIDC
  • GENE

Journal Title:



Volume 9, Number 8


, Pages e99811-e99811

Type of Work:

Article | Final Publisher PDF


During sporulation in Bacillus subtilis, the onset of activity of the late forespore-specific sigma factor σ<sup>G</sup> coincides with completion of forespore engulfment by the mother cell. At this stage, the forespore becomes a free protoplast, surrounded by the mother cell cytoplasm and separated from it by two membranes that derive from the asymmetric division septum. Continued gene expression in the forespore, isolated from the surrounding medium, relies on the SpoIIIA-SpoIIQ secretion system assembled from proteins synthesised both in the mother cell and in the forespore. The membrane protein insertase SpoIIIJ, of the YidC/Oxa1/Alb3 family, is involved in the assembly of the SpoIIIA-SpoIIQ complex. Here we show that SpoIIIJ exists as a mixture of monomers and dimers stabilised by a disulphide bond. We show that residue Cys134 within transmembrane segment 2 (TM2) of SpoIIIJ is important to stabilise the protein in the dimeric form. Labelling of Cys134 with a Cys-reactive reagent could only be achieved under stringent conditions, suggesting a tight association at least in part through TM2, between monomers in the membrane. Substitution of Cys134 by an Ala results in accumulation of the monomer, and reduces SpoIIIJ function in vivo. Therefore, SpoIIIJ activity in vivo appears to require dimer formation.

Copyright information:

© 2014 Côrte et al.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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