Abstract
Aurora B is a serine/threonine protein kinase. Its enzymatic activity is required for accurate chromosome segregation, spindle midzone stability and cell division. Aurora B kinase is always in association with the activator protein, INCENP, and full activity requires auto-phosphorylation of both, a threonine in the activation loop of Aurora B and the serines in the TSS-motif (Threonine-Serine-Serine) present on INCENP. Structural studies have revealed profound conformational changes in the enzyme complex upon auto-phosphorylation and initial hydrogen- deuterium exchange studies indicate structural dynamic changes associated with auto-phosphorylation. In this study, we have used molecular dynamics to simulate three phosphorylation states of the enzyme complex (non-phosphorylated enzyme complex, enzyme complex phosphorylated only in the activation loop of Aurora B and enzyme complex phosphorylated in both loop of Aurora B and INCENP). We found that phosphorylation has a profound impact on the structure and dynamics of Aurora B/INCENP-complex inducing allosteric communication between INCENP and Aurora B. Upon phosphorylation of the threonine in the activation loop of Aurora B, INCENP adopts a dramatic conformational change and comes into close contact with the activation loop region. Other analyzed regions undergoing noticeable structural changes upon phosphorylation are the active site where ATP becomes more stably bound, the activation loop that becomes more rigid and the αG-helix experiencing a shift towards the core of Aurora B. Principle component analysis revealed a synchronized motion in the fully phosphorylated state of the enzyme complex with coupled open-close and activation loop motions, a feature that might contribute to increased activity. The insights into regulation of Aurora B/INCENP-complex provided in our study might help towards generating a more specific inhibitor of Aurora B in future cancer treatment.