ParAB Partition Dynamics in Firmicutes: Nucleoid Bound ParA Captures and Tethers ParB-Plasmid Complexes

PLoS One. 2015 Jul 10;10(7):e0131943. doi: 10.1371/journal.pone.0131943. eCollection 2015.

Abstract

In Firmicutes, small homodimeric ParA-like (δ2) and ParB-like (ω2) proteins, in concert with cis-acting plasmid-borne parS and the host chromosome, secure stable plasmid inheritance in a growing bacterial population. This study shows that (ω:YFP)2 binding to parS facilitates plasmid clustering in the cytosol. (δ:GFP)2 requires ATP binding but not hydrolysis to localize onto the cell's nucleoid as a fluorescent cloud. The interaction of (δ:CFP)2 or δ2 bound to the nucleoid with (ω:YFP)2 foci facilitates plasmid capture, from a very broad distribution, towards the nucleoid and plasmid pairing. parS-bound ω2 promotes redistribution of (δ:GFP)2, leading to the dynamic release of (δ:GFP)2 from the nucleoid, in a process favored by ATP hydrolysis and protein-protein interaction. (δD60A:GFP)2, which binds but cannot hydrolyze ATP, also forms unstable complexes on the nucleoid. In the presence of ω2, (δD60A:GFP)2 accumulates foci or patched structures on the nucleoid. We propose that (δ:GFP)2 binding to different nucleoid regions and to ω2-parS might generate (δ:GFP)2 gradients that could direct plasmid movement. The iterative pairing and unpairing cycles may tether plasmids equidistantly on the nucleoid to ensure faithful plasmid segregation by a mechanism compatible with the diffusion-ratchet mechanism as proposed from in vitro reconstituted systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / genetics
  • Bacillus subtilis / metabolism*
  • Bacterial Proteins / metabolism*
  • DNA, Bacterial / genetics
  • DNA, Bacterial / metabolism
  • Gene Expression Regulation, Bacterial
  • Green Fluorescent Proteins / metabolism
  • Nucleosomes / genetics
  • Plasmids / genetics
  • Plasmids / metabolism*
  • Protein Binding
  • Protein Transport
  • Time-Lapse Imaging

Substances

  • Bacterial Proteins
  • DNA, Bacterial
  • Nucleosomes
  • chromosome partition proteins, bacterial
  • Green Fluorescent Proteins

Grants and funding

This work was supported in part by the Ministerio de Economía y Competitividad, Dirección General de Investigación grants BFU2012-39879-C02-01 to J.C.A. and BFU2012-39879-C02-02 to S.A., and by the Comunidad de Madrid grant S2009MAT-1507 to J.C.A, and BIO0260-2006 to S.A. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.