CTP and parS coordinate ParB partition complex dynamics and ParA-ATPase activation for ParABS-mediated DNA partitioning
James A. Taylor, Yeonee Seol, Jagat B. Budhathoki, Keir C. Neuman, Kiyoshi Mizuuchi
Abstract
ParABS partition systems, comprising the centromere-like DNA sequence parS , the parS -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 ParB F and parS F move by generating and following a local concentration gradient of nucleoid-bound ParA F . However, the process through which ParB F activates ParA F -ATPase has not been defined. We studied CTP- and parS F -modulated ParA F –ParB F complex assembly, in which DNA-bound ParA F -ATP dimers are activated for ATP hydrolysis by interacting with two ParB F N-terminal domains. CTP or parS F enhances the ATPase rate without significantly accelerating ParA F –ParB F complex assembly. Together, parS F and CTP accelerate ParA F –ParB F assembly without further significant increase in ATPase rate. Magnetic-tweezers experiments showed that CTP promotes multiple ParB F loading onto parS F -containing DNA, generating condensed partition complex-like assemblies. We propose that ParB F in the partition complex adopts a conformation that enhances ParB F –ParB F and ParA F –ParB F interactions promoting efficient partitioning.