Has a role in chromosome segregation. May provide a dynamic connection between kinetochore microtubules and kinetochore chromatin. Negatively regulates mis12. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 manganese ions per subunit. Interacts with sts5, ekc1 and mis12. Associated with chromatin. Belongs to the PPP phosphatase family. PP-6 (PP-V) subfamily.