Required both for recombination and for the repair of DNA damage caused by X-rays. Binds to single and double-stranded DNA, in the presence of magnesium, and exhibits DNA-dependent ATPase activity. Promotes DNA strand annealing and strand exchange via DNA recombinase activity and forms helical nucleoprotein filaments. Interacts with rad22, rad54, rdh54, rhp54, rti1, swi2 and swi5. Forms homooiligomers. Belongs to the RecA family. RAD51 subfamily.