Involved in DNA double-strand break (DSB) repair. Involved in mating type switching and has a role in choosing the sister chromatid for recombinational repair. Also has a role in telomere length maintenance. Binds 1 zinc ion per homodimer. Heterodimer (By similarity). Interacts with the rad21 cohesin complex. Forms a multisubunit endonuclease complex, MRN, together with nbn and rad32. The zinc-hook, which separates the large intramolecular coiled coil regions, contains 2 Cys residues that coordinate one molecule of zinc with the help of the 2 Cys residues of the zinc-hook of another rad50 molecule, thereby forming a V-shaped homodimer. Belongs to the SMC family. RAD50 subfamily.