The Exodeoxyribonuclease V enzyme is a multi-subunit enzyme comprised of the proteins RecB, RecC (this family) and RecD. This enzyme plays an important role in homologous genetic recombination, repair of double strand DNA breaks resistance to UV irradiation and chemical DNA-damage. The enzyme (EC:3.1.11.5) catalyses ssDNA or dsDNA-dependent ATP hydrolysis, hydrolysis of ssDNA or dsDNA and unwinding of dsDNA [1]. This subunit recognises and binds DNA forks containing Chi sequences in a sequence specific manner while Chi interactions with the phosphodiester backbone (mainly arginine side chains) stabilise the twisted conformation of the DNA. These interactions induce conformational changes that switch RecBCD from bacteriophage destruction and CRISPR spacer acquisition, to constructive host DNA repair [2].

1: The initiation and control of homologous recombination in Escherichia coli. Smith GR, Amundsen SK, Dabert P, Taylor AF; Philos Trans R Soc Lond B Biol Sci 1995;347:13-20. PMID:7746848

2: A conformational switch in response to Chi converts RecBCD from phage destruction to DNA repair. Cheng K, Wilkinson M, Chaban Y, Wigley DB; Nat Struct Mol Biol. 2020;27:71-77. PMID:31907455