Levinson Lab

We used a combination of double electron-electron resonance (DEER) spectroscopy, paramagnetic relaxation enhancement NMR, and fluorescence to study allosteric activation of cyclin-dependent kinase 2 in solution. We showed that phosphorylation of Cdk2 on the activation loop enhances allosteric coupling between the cyclin subunit and the kinase, and demonstrate that this allosteric coupling underlies the selective recognition of CDK inhibitors.

We used a new time-resolved FRET based method to profile the conformational effects of a large panel of Aurora kinase inhibitors on Aurora A. The results show clearly for the first time that the preference of inhibitors for the DFG-in or DFG-out states is the dominant determinant of selectivity, and that different DFG-out inhibitors differ by two orders of magnitude in their preference for the DFG-out state. This suggests that many of these inhibitors selectively target different cellular pools of Aurora A, with important implications for the clinical use of Aurora A inhibitors currently in trials.

We used a diverse range of spectroscopic methods combined with long timescale molecular dynamics simulations to show that phosphorylation of the activation loop does not trap Aurora kinase A in the active DFG-in state as previously thought, and that the loop instead continues to transition between the DFG-in and DFG-out states. Activation occurs through tuning of the catalytic activity of the DFG-in subpopulation through a phosphorylation-driven switch from a previously undetected autoinhibited DFG-in substate to the active DFG-in substate.

We used an infrared probe to show that allosteric activation of the mitotic kinase Aurora A by the spindle-associated protein Tpx2 is a two-step process, involving both a conformatonal shift towards the active DFG-In state, and an enhancement of the intrinsic activity of the DFG-In state through tuning of a novel allosteric network mediated by structured water molecules.

Type I kinase inhibitors exploit structured water molecules in the ATP-binding site to recognize their kinase targets. These interactions turn out to be energetically significant and make a big contribution to the selectivity that inhibitors display for different kinases.

Bosutinib is a second-generation Abl kinase inhibitor used in the treatment of chronic myeloid leukemia. We determined the first crystal structure of this drug bound to the Abl kinase domain. The structure explains the effects of several resistance mutations that arise in patients during tyrosine kinase inhibitor therapy.

Src kinase, the prototypical oncogene, is catalytically inactivated through phosphorylation on a C-terminal tyrosine residue. The kinase responsible, Csk, only phosphorylates the Src kinases. We illuminated the structural basis for this unusual specificity by cocrystallizing the two proteins.

The distantly related tyrosine kinases Src and Abl were previously thought to have unrelated allosteric activation mechanisms. Here we showed that Abl can in fact adopt an inactive conformation that looks almost identical to the canonical inactive conformation of Src, demonstrating that the conformational states that protein kinases adopt are broadly conserved across this protein family.