RuvABC is a complex of three proteins that mediate branch migration and resolve the Holliday junction created during homologous recombination in bacteria. As such, RuvABC is critical to bacterial DNA repair.
thumb|320px|right|RuvA-RuvB complex heteromer, Thermus thermophilus
RuvA and RuvB bind to the four strand DNA structure formed in the Holliday junction intermediate, and migrate the strands through each other, using a putative spooling mechanism. Replication restart is a multi-step process in E. coli that requires the sequential action of several proteins. When the progress of the replication fork is impeded, the single-stranded binding protein and RecG helicase along with the RuvABC complex are required for rescue.
RuvA
RuvA is a DNA-binding protein that binds Holliday junctions with high affinity. The structure of the complex has been variously elucidated through X-ray crystallography and EM data. RuvA forms a tetramer that binds to the Holliday junction and forces it into a planar configuration. RuvC can be bound to the complex in either orientation, therefore resolving Holliday junctions in either a horizontal or vertical manner. One theory is that a RuvA tetramer binds only to one side of the DNA, leaving an exposed face for RuvC to bind to. An alternative theory is that RuvA does not maintain the shell like structure it initially forms around the junction, but rather opens up to allow RuvC to access the DNA.