PMF-1 is a 205 amino acid protein involved in kinetochore formation. Localized to the nucleus, PMF-1 contains a coiled-coil domain which interacts with the leucine-zipper domain of Nrf2. This interaction regulates the transcription of SSAT, a regulatory enzyme for polyamine catabolism. PMF-1 is also a component of the MIS12 complex, which is required for kinetochore formation and chromosomal alignment and segregation. PMF-1 is expressed at highest levels in skeletal muscle and heart, with moderate expression in liver and kidney. PMFBP1 (Polyamine-modulated factor 1-binding protein 1) is a 1022 amino acid protein that binds PMF-1 and may be involved in general organization of the cytoskeleton. Due to evidence that PMFBP1 may play a role in sperm tail morphology, it may therefore affect fertility. There are three isoforms of PMFBP1 that are produced as a result of alternative splicing events.