Crossover junction endodeoxyribonuclease

During cell growth and meiosis, DNA double-strand breaks (DSBs) often occur, and are usually repaired by homologous recombination.

E. coli RuvC, a Crossover junction endodeoxyribonuclease, is a small protein of about 20 kD, and its active form is a dimer that requires and binds a magnesium ion [1].

[7] A Holliday junction resolvase enzyme has also been identified in archaea in Pyrococcus furiosus cells - it is encoded by a gene called hjc and is composed of 123 amino acids [8] .

These enzymes are highly selective for branched DNA, although induced fit occurs in the enzyme-substrate (resolvase-Holloday Junction) complex formation.

Analysis of crossover junction endodeoxyribonucleases from bacteriophages (T7 endonuclease I), bacteria (RuvC), fungi (GEN1) and humans (hMus81-Eme1) have revealed that the enzymes function in dimers,[11] and part of the resolution reaction takes place in a partially dissociated enzyme-substrate intermediate.

Holliday junction resolution catalyzed by crossover junction endodeoxyribonuclease. Left: First, four strands of DNA (two black and two white) combine to form two double stranded DNA molecules at a Holliday junction. Center: Next, substrate form a complex with crossover junction endodeoxyribonuclease complex for Holliday junction resolution. Right: Finally, completion of Holliday Junction Resolution results in recombinant DNA. Diagram generated based on Wyatt et al. [ 4 ]
Archaea crossover junction endodeoxyribonuclease in complex with Holliday Junction DNA. Generated with 4LD0.pdb. [ 6 ]