Molecule of the Month: c-Abl Protein Kinase and Imatinib
Protein kinases are being targeted by new anti-cancer drugs
Structures Open the Door
Disordered Yet Not Dysfunctional
A Cancerous Combination
Exploring the Structure
c-Abl and c-Kit
Imatinib blocks the ATP-binding site of the c-Abl kinase domain, stopping its action. Several regions in the kinase are important for its function and inhibition by imatinib, as seen in structures of the kinase with ADP (PDB ID 2g2i) and with imatinib (PDB ID 2hyy). The “activation loop” closes over the active site and controls access, and is regulated by a tyrosine that may be phosphorylated. The “gatekeeper” threonine, the “DFG Motif”, and several hydrogen bonding amino acids (not shown) are involved in specific interactions with imatinib, helping make the drug more selective. However, the drug is not perfectly selective, but fortuitously this could be turned to advantage. Imatinib also inhibits c-Kit (PDB ID 1t46), an oncoprotein tyrosine kinase that causes gastrointestinal stromal tumors (GIST). c-Kit and c-Abl are closely related kinases, allowing imatinib to be effective against both. To explore these structures in further detail, click on the JSmol tab.
Topics for Further Discussion
- To take a closer look at the kinase and regulatory domains, visit the annotated visualization in the 3D Protein Structure View.
- Imatinib is effective against a range of kinases, including the spleen tyrosine kinase (Syk), which is involved in immunoreceptor signaling in hematopoietic cells. Imatinib inhibits Syk in an unusually compact U-shaped conformation, as seen in PDB ID 1xbb.
July 2023, Allison Abel, Darlene R. Malave-Ramos, Bhavya Soni, Christopher Thai, Amy Wu-Wu, David S. Goodsell and Stephen K. Burleyhttp://doi.org/10.2210/rcsb_pdb/mom_2023_7