CTP and < i > parS < /i > coordinate ParB partition complex dynamics and ParA-ATPase activation for ParABS-mediated DNA partitioning

ParABS partition systems, comprising the centromere-like DNA sequenceparS, theparS-binding ParB-CTPase and the nucleoid-binding ParA-ATPase, ensure faithful segregation of bacterial chromosomes and low-copy-number plasmids. F-plasmid partition complexes containing ParBF andparSF move by generating and following a local concentration gradient of nucleoid-bound ParAF. However, the process through which ParBF activates ParAF-ATPase has not been defined. We studied CTP- andparSF-modulated ParAF-ParBF complex assembly, in which DNA-bound ParAF-ATP dimers are activated for ATP hydrolysis by interacting with two ParBF N-terminal domains. CTP orparSF enhances the ATPase rate without significantly accelerating ParAF-ParBF complex assembly. Together,parSF and CTP accelerate ParAF-ParBF assembly without further significant increase in ATPase rate. Magnetic-tweezers experiments showed that CTP promotes multiple ParBF loading ontoparSF-containing DNA, generating condensed partition complex-like assemblies. We propose that ParBF in the partition complex adopts a conformation that enhances ParBF-ParBF and ParAF-ParBF interactions promoting efficient partitioning.
Source: eLife - Category: Biomedical Science Tags: Cell Biology Microbiology and Infectious Disease Source Type: research