Part of the Rad50/Mre11 complex, which is involved in the early steps of DNA double-strand break (DSB) repair. The complex may facilitate opening of the processed DNA ends to aid in the recruitment of HerA and NurA. Rad50 controls the balance between DNA end bridging and DNA resection via ATP-dependent structural rearrangements of the Rad50/Mre11 complex. Binds 1 zinc ion per homodimer. Homodimer. Forms a heterotetramer composed of two Mre11 subunits and two Rad50 subunits. The two conserved Cys that bind zinc constitute the zinc-hook, which separates the large intramolecular coiled coil regions. The 2 Cys residues 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.