Component of the kinetochore, a multiprotein complex that assembles on centromeric DNA and attaches chromosomes to spindle microtubules, mediating chromosome segregation and sister chromatid segregation during meiosis and mitosis. Component of the inner kinetochore constitutive centromere-associated network (CCAN), which serves as a structural platform for outer kinetochore assembly (PubMed:10398680). Required for the localization of cnp1 to the centromere (PubMed:10864871). Component of the inner kinetochore constitutive centromere-associated network (CCAN) (also known as central kinetochore Sim4 complex in fission yeast), which is composed of at least cnl2, cnp3, cnp20, fta1, fta2, fta3, fta4, fta6, fta7, mal2, mhf1, mhf2, mis6, mis15, mis17, sim4 and wip1 (PubMed:16079914). Interacts with cnp1, sim4, mis15 and mis17 (PubMed:10864871, PubMed:12719471, PubMed:15369671). Belongs to the CENP-I/CTF3 family.