Download MendeleyCocrystallization of the Src-Family Kinase Hck with the ATP-Site Inhibitor A-419259 Stabilizes an Extended Activation Loop Conformation.
Selzer, A.M., Alvarado, J.J., Smithgall, T.E.(2024) Biochemistry 63: 2594-2601
- PubMed: 39315638
- DOI: https://doi.org/10.1021/acs.biochem.4c00323
- Primary Citation of Related Structures:
9BYJ - PubMed Abstract:
Hematopoietic cell kinase (Hck) is a member of the Src kinase family and is a promising drug target in myeloid leukemias. Here, we report the crystal structure of human Hck in complex with the pyrrolopyrimidine inhibitor A-419259, determined at a resolution of 1.8 Å. This structure reveals the complete Hck active site in the presence of A-419259, including the αC-helix, the DFG motif, and the activation loop. A-419259 binds at the ATP-site of Hck and induces an overall closed conformation of the kinase with the regulatory SH3 and SH2 domains bound intramolecularly to their respective internal ligands. A-419259 stabilizes the DFG-in/αC-helix-out conformation observed previously with Hck and the pyrazolopyrimidine inhibitor PP1 (PDB: 1QCF). However, the activation loop conformations are distinct, with PP1 inducing a folded loop structure with the tyrosine autophosphorylation site (Tyr416) pointing into the ATP binding site, while A-419259 stabilizes an extended loop conformation with Tyr416 facing out into the solvent. Autophosphorylation also induces activation loop extension and significantly reduces the Hck sensitivity to PP1 but not A-419259. In cancer cells where Hck is constitutively active, the extended autophosphorylation loop may render Hck more sensitive to inhibitors like A-419259 which prefer this kinase conformation. More generally, these results provide additional insight into targeted kinase inhibitor design and how conformational preferences of inhibitors may impact selectivity and potency.
Organizational Affiliation:
Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, Pittsburgh, Pennsylvania PA 15219, United States.
