title: VX680 binding in Aurora A: π-π interactions involving the conserved aromatic amino acid of the flexible glycine-rich loop.
abstract: The regulation of protein kinases requires flexibility, especially near the ATP binding site. The cancer drug target Aurora A is inhibited by the ATP site inhibitor VX680, and published crystal structures show two distinct conformations. In one, a refolded glycine-rich loop creates a stacked π-π interaction between the conserved aromatic residue of the glycine-rich loop hairpin turn (F144) and the inhibitor. This refolding, associated with binding to a peptide derived from the cofactor TPX2, is absent in the other structure. We use surface plasmon resonance to measure VX680 binding to native and mutant F144A Aurora A kinase domains, with and without the TPX2 peptide. Results show that the F144 aromatic side chain contributes 2 kcal/mol to the VX680 binding energy, independent of the TPX2 peptide. This indicates that distinct VX680 bound conformations of Aurora A cannot be simply correlated with TPX2 binding and that Aurora A retains flexibility when inhibitor-bound. Molecular dynamics simulations show that alternate geometries for the π-π interactions are feasible in the absence of the rigidifying packing interactions seen in the crystal lattice.
authors.affiliation: NORSTRUCT, Department of Chemistry, University of Tromsø, 9037 Tromsø, Norway.
authors.forename: Taianá M
authors.initials: TM
authors.lastname: Oliveira
authors.forename: Rafi
authors.initials: R
authors.lastname: Ahmad
authors.forename: Richard A
authors.initials: RA
authors.lastname: Engh
mesh_terms: D024322:Amino Acids, Aromatic / Q000737:chemistry*; D064127:Aurora Kinases; D001665:Binding Sites; D018360:Crystallography, X-Ray; D005998:Glycine / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D010879:Piperazines / Q000737:chemistry*; D017510:Protein Folding / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D003521:Cyclopropanes; D011720:Pyrazoles; D011743:Pyrimidines
chemical_list: D024322:Amino Acids, Aromatic; D064127:Aurora Kinases; D005998:Glycine; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; C484810:tozasertib; D003521:Cyclopropanes; D011720:Pyrazoles; D011743:Pyrimidines