The central intermediate formed during mitotic and meiotic recombination is a four stranded DNA structure, also known as the Holliday junction (HJ), and its efficient resolution is essential for proper segregation of chromosomes. Resolution of HJs is mediated by a diverse group of DNA structure specific endonucleases known as Holliday junction resolvases (HJR) [1]. This entry is specific for RuvX also known as YqgF a family of nucleases which resolves the Holliday junction intermediates in genetic recombination[2-3]. Studies carried out in M. tuberculosis, have shown that YqgF/RuvX is a genuine HJR analogous to RuvC from E. coli. Furthermore, a single cysteine present in M. tuberculosis RuvX was found to be required for disulfide-bond mediated intermolecular dimerization and HJ resolution activity, suggesting that M. tuberculosis RuvX has adapted its YqgF protein to function like a typical RuvC family HJR [1].

1: Mycobacterium tuberculosis RuvX is a Holliday junction resolvase formed by dimerisation of the monomeric YqgF nuclease domain. Nautiyal A, Rani PS, Sharples GJ, Muniyappa K; Mol Microbiol. 2016;100:656-674. PMID:26817626

2: Holliday junction resolvases and related nucleases: identification of new families, phyletic distribution and evolutionary trajectories. Aravind L, Makarova KS, Koonin EV; Nucleic Acids Res. 2000;28:3417-3432. PMID:10982859

3: 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