RuvA domain 2-like superfamily

In prokaryotes, RuvA, RuvB, and RuvC process the universal DNA intermediate of homologous recombination, termed Holliday junction. The tetrameric DNA helicase RuvA specifically binds to the Holliday junction and facilitates the isomerization of the junction from the stacked folded configuration to the square-planar structure [12408833]. In the RuvA tetramer, each subunit consists of three domains, I, II and III, where I and II form the major core that is responsible for Holliday junction binding and base pair rearrangements of Holliday junction executed at the crossover point, whereas domain III regulates branch migration through direct contact with RuvB. Domain 2 has a SAM (sterile alpha motif)-like alpha bundle fold that occurs as a duplication containing two helix-hairpin-helix (HhH) motifs.

The C-terminal domain (CTD) of the excision repair protein UvrC shows structural similarity to RuvA domain 2. The CTD of UvrC is essential for 5' incision in the prokaryotic nucleotide excision repair process, and acts to mediate structure-specific binding to single-stranded-double-stranded junction DNA [12426397].

Domain 3 of NAD+-dependent DNA ligase consists of a duplication of two RuvA-like domains (four HhH motifs), and also contains a zinc-finger subdomain. DNA ligases catalyze the crucial step of joining the breaks in duplex DNA during DNA replication, repair and recombination, utilizing either ATP or NAD+ as a cofactor [10698952].