Bacterial actin: architecture of the ParMRC plasmid DNA partitioning complex.

Journal article

The R1 plasmid employs ATP-driven polymerisation of the actin-like protein ParM to move newly replicated DNA to opposite poles of a bacterial cell. This process is essential for ensuring accurate segregation of the low-copy number plasmid and is the best characterised example of DNA partitioning in prokaryotes. In vivo, ParM only forms long filaments when capped at both ends by attachment to a centromere-like region parC, through a small DNA-binding protein ParR. Here, we present biochemical and electron microscopy data leading to a model for the mechanism by which ParR-parC complexes bind and stabilise elongating ParM filaments. We propose that the open ring formed by oligomeric ParR dimers with parC DNA wrapped around acts as a rigid clamp, which holds the end of elongating ParM filaments while allowing entry of new ATP-bound monomers. We propose a processive mechanism by which cycles of ATP hydrolysis in polymerising ParM drives movement of ParR-bound parC DNA. Importantly, our model predicts that each pair of plasmids will be driven apart in the cell by just a single double helical ParM filament.

Authors: Salje, J; Löwe, J

• Journal: EMBO journal
• Volume: 27
• Issue: 16
• Pages: 2230-2238
• Publication date: 2008-08-01
• DOI: 10.1038/emboj.2008.152
• EISSN: 1460-2075
• ISSN: 0261-4189
• Language: English
• Keywords: Models, Molecular; DNA Topoisomerase IV; Promoter Regions, Genetic; Protein Binding; Protein Structure, Secondary; Plasmids; Actins; DNA, Bacterial; Peptides; Escherichia coli Proteins