A protein complex involved in the assembly of the mitotic checkpoint complex that in turn inhibits the anaphase promoting complex/cyclosome (APC/C). The MAD1 dimer recruits the open form of MAD2 (O-MAD2) turning it into the closed form (C-MAD2) upon binding. C-MAD2 inhibits CDC20, a member of the APC/C, upon release from the MAD1-MAD2 complex.
MAD1-MAD2 complex