The Kinesins constitute a large family of microtubule-dependent motor proteins which are responsible for the distribution of numerous organelles, vesicles and macromolecular complexes throughout the cell. Individual Kinesin members play crucial roles in cell division, intracellular transport and membrane trafficking events, including endocytosis and transcytosis. MPP1 (M-phase phosphoprotein 1), also known as KIF20B (kinesin family member 20B), MPHOSPH1 or KRMP1, is a 1,820 amino acid protein that localizes to both the nucleus and the cytoplasm and contains one kinesin-motor domain. Expressed in kidney, brain, testis and ovary, MPP1 functions as a plus-end directed motor enzyme that interacts with Pin1 and is required for the completion of cytokinesis. MPP1, which exists as multiple alternatively spliced isoforms termed 1-5, is subject to post-translational phosphorylation, probably by ATM or ATR.