Part of the Rad50/Mre11 complex, which is involved in the early steps of DNA double-strand break (DSB) repair (PubMed:11029422, PubMed:18957200). The complex may facilitate opening of the processed DNA ends to aid in the recruitment of HerA and NurA (PubMed:18957200). Rad50 controls the balance between DNA end bridging and DNA resection via ATP-dependent structural rearrangements of the Rad50/Mre11 complex (PubMed:24493214). The ATP-bound conformation promotes DNA end binding and end tethering, and alters Mre11 nuclease activity (PubMed:24493214). ATP hydrolysis promotes both Mre11 activity as well as HerA/NurA activity (PubMed:24493214). Has also reversible adenylate kinase activity (PubMed:17349953). Binds 1 zinc ion per homodimer. The adenylate kinase inhibitor P(1),P(5)-di(adenosine-5') pentaphosphate (Ap5A) inhibits adenylate kinase activity, but does not affect ATPase activity. Homodimer (PubMed:10892749, PubMed:14698290). Forms a heterotetramer composed of two Mre11 subunits and two Rad50 subunits (PubMed:11371344, PubMed:21441914, PubMed:22102415). Homodimerization is promoted by ATP binding (PubMed:10892749). Binding of ATP induces a closed, compact conformation of the Rad50/Mre11 complex. ATP hydrolysis opens the complex. 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.