Essential component of the MRN complex, a complex that possesses single-stranded DNA endonuclease and 3' to 5' exonuclease activities, and plays a central role in double-strand break (DSB) repair. The complex participates in processes such as DNA recombination, DNA repair, genome stability, telomere integrity and meiosis. The MRN complex may protect telomeres by facilitating recruitment of HOAP and HP1 at chromosome ends. In the complex, it mediates the ATP-binding and is probably required to bind DNA ends and hold them in close proximity. Binds 1 zinc ion per homodimer. Homodimer. Probable component of the MRN complex with mre11 (By similarity). Uniformly distributed along mitotic chromosomes. 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. The two heads of the homodimer, which constitute the ATP-binding domain, interact with the MRE11 homodimer (By similarity). Death during pupal stage, possibly due to the accumulation of DNA DSBs and the induction of apoptosis in third instar larvae. Belongs to the SMC family. RAD50 subfamily. Truncated N-terminus. Extended N-terminus.