3ESL CELL CYCLE, BUB1, MITOTIC SPINDLE CHECKPOINT, TPR MOTIF, ALL-ALPHA DOMAIN, MAD3-LIKE DOMAIN, CHROMOSOME INSTABILITY, ATP- BINDING, KINASE, NUCLEOTIDE-BINDING, NUCLEUS, PHOSPHORYLATION, SERINE/THREONINE-PROTEIN KINASE, TRANSFERASE, KINETOCHORE LOCALIZATION, PHOSPHOPROTEIN CRYSTAL STRUCTURE OF THE CONSERVED N-TERMINAL DOMAIN OF THE MITOTIC CHECKPOINT COMPONENT BUB1