Aurora A on the Mitotic Spindle Is Activated by the Way It Holds Its Partner

An exciting study in this issue (Bayliss et al., 2003) reveals how binding of the microtubule associated protein TPX2 to the mitotic kinase Aurora A induces a conformational change. This moves the phosphorylated activation domain into a more compact position within the kinase core, providing a better substrate binding platform and hiding the activating phosphoryl group from attack by PP1.