This entry includes endodeoxyribonucleases found in bacteria, such as RuvC. RuvC is a small protein of about 20 kD. It requires and binds a magnesium ion. The structure of E. coli RuvC is a 3-layer alpha-beta sandwich containing a 5-stranded beta-sheet sandwiched between 5 alpha-helices [2]. The Escherichia coli RuvC gene is involved in DNA repair and in the late step of RecE and RecF pathway recombination [1]. RuvC protein (EC:3.1.22.4) cleaves cruciform junctions, which are formed by the extrusion of inverted repeat sequences from a super-coiled plasmid and which are structurally analogous to Holliday junctions, by introducing nicks into strands with the same polarity. The nicks leave a 5'terminal phosphate and a 3'terminal hydroxyl group which are ligated by E. coli or Bacteriophage T4 DNA ligases. Analysis of the cleavage sites suggests that DNA topology rather than a particular sequence determines the cleavage site. RuvC protein also cleaves Holliday junctions that are formed between gapped circular and linear duplex DNA by the function of RecA protein. The active form of RuvC protein is a dimer. This is mechanistically suited for an endonuclease involved in swapping DNA strands at the crossover junctions. It is inferred that RuvC protein is an endonuclease that resolves Holliday structures in vivo [1].

1: Escherichia coli RuvC protein is an endonuclease that resolves the Holliday structure. Iwasaki H, Takahagi M, Shiba T, Nakata A, Shinagawa H; EMBO J. 1991;10:4381-4389. PMID:1661673

2: Preliminary crystallographic study of Escherichia coli RuvC protein. An endonuclease specific for Holliday junctions. Ariyoshi M, Vassylyev DG, Iwasaki H, Fujishima A, Shinagawa H, Morikawa K; J Mol Biol. 1994;241:281-282. PMID:8057369