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

ABSTRACT: In Firmicutes, small homodimeric ParA-like (?2) and ParB-like (?2) 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 (?:YFP)2 binding to parS facilitates plasmid clustering in the cytosol. (?:GFP)2 requires ATP binding but not hydrolysis to localize onto the cell's nucleoid as a fluorescent cloud. The interaction of (?:CFP)2 or ?2 bound to the nucleoid with (?:YFP)2 foci facilitates plasmid capture, from a very broad distribution, towards the nucleoid and plasmid pairing. parS-bound ?2 promotes redistribution of (?:GFP)2, leading to the dynamic release of (?:GFP)2 from the nucleoid, in a process favored by ATP hydrolysis and protein-protein interaction. (?D60A:GFP)2, which binds but cannot hydrolyze ATP, also forms unstable complexes on the nucleoid. In the presence of ?2, (?D60A:GFP)2 accumulates foci or patched structures on the nucleoid. We propose that (?:GFP)2 binding to different nucleoid regions and to ?2-parS might generate (?: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.

SUBMITTER: Lioy VS 

PROVIDER: S-EPMC4498918 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature