An autoinhibitory tyrosine motif in the cell-cycle-regulated Nek7 kinase is released through binding of Nek9.
Bottom Line: Tyrosine mutants of Nek7 and the related kinase Nek6 are constitutively active.The activity of Nek6 and Nek7, but not the tyrosine mutant, is increased by interaction with the Nek9 noncatalytic C-terminal domain, suggesting a mechanism in which the tyrosine is released from its autoinhibitory position.The autoinhibitory conformation is common to three Neks and provides a potential target for selective kinase inhibitors.
Affiliation: Institute of Cancer Research, London, UK.
Mitosis is controlled by multiple protein kinases, many of which are abnormally expressed in human cancers. Nek2, Nek6, Nek7, and Nek9 are NIMA-related kinases essential for proper mitotic progression. We determined the atomic structure of Nek7 and discovered an autoinhibited conformation that suggests a regulatory mechanism not previously described in kinases. Additionally, Nek2 adopts the same conformation when bound to a drug-like molecule. In both structures, a tyrosine side chain points into the active site, interacts with the activation loop, and blocks the alphaC helix. Tyrosine mutants of Nek7 and the related kinase Nek6 are constitutively active. The activity of Nek6 and Nek7, but not the tyrosine mutant, is increased by interaction with the Nek9 noncatalytic C-terminal domain, suggesting a mechanism in which the tyrosine is released from its autoinhibitory position. The autoinhibitory conformation is common to three Neks and provides a potential target for selective kinase inhibitors.
Related in: MedlinePlus
Mentions: We crystallized the apo-form, full-length (35 kDa) human Nek7 protein and determined the structure to 2.1 Å. We also soaked the apo-form crystals with ADP and determined the ADP-bound structure to 2.3 Å resolution. Both structures have excellent refinement and geometry statistics (Table 1). The protein structures exhibit the canonical bilobal fold and are virtually identical. Residues 20–300 were modeled, with the exception of the disordered activation loop (residues 181–198) and a small loop (residues 237–240) (Figure 1A). The Gly-rich loop was more ordered in the ADP-bound structure, consistent with an interaction with the ADP ligand. The overall conformation is that of an inactive kinase with the αC helix, DLG motif, and activation loop displaced from the usual configuration observed in active enzymes (Figures 1B and 1C).