The N-terminal domain of RAD21 contains two α-helices which forms a three helix bundle with the coiled coil of SMC3. The central region of RAD21 is thought to be largely unstructured but contains several binding sites for regulators of cohesin. This includes a binding site for SA1 or SA2, recognition motifs for separase cleavage and a region that is competitively bound by PDS5A, PDS5B or NIPBL. The C-terminal domain of RAD21 forms a winged helix that binds two β-sheets in the Smc1 head domain.