Exploring the Conformational Landscape and Stability of Aurora A Using Ion-Mobility Mass Spectrometry and Molecular Modeling.

Protein kinase inhibitors are highly effective in treating diseases driven by aberrant kinase signaling and as chemical tools to help dissect the cellular roles of kinase signaling complexes. Evaluating the effects of binding of small molecule inhibitors on kinase conformational dynamics can assist in understanding both inhibition and resistance mechanisms. Using gas-phase ion-mobility mass spectrometry (IM-MS), we characterize changes in the conformational landscape and stability of the protein kinase Aurora A (Aur A) driven by binding of the physiological activator TPX2 or small molecule inhibition. Aided by molecular modeling, we establish three major conformations, the relative abundances of which were dependent on the Aur A activation status: one highly populated compact conformer similar to that observed in most crystal structures, a second highly populated conformer possessing a more open structure infrequently found in crystal structures, and an additional low-abundance conformer not currently represented in the protein databank. Notably, inhibitor binding induces more compact configurations of Aur A, as adopted by the unbound enzyme, with both IM-MS and modeling revealing inhibitor-mediated stabilization of active Aur A.