Inactive kinase conformations

Liu Y, Gray NS. Rational design of inhibitors that bind to inactive kinase conformations. NaLChem Biol 2006 2 358-364. 

Arqule (www.arqule.com) have recently published work on the potential advantages of targeting autoinhibited, inactive kinase conformations. First reported was the discovery of ARQ 197 (14), Figure 2.9, a cMET inhibitor which was shown to bind to an inactive kinase conformation and is currently in Phase III studies.19... 

The availabUity of the DFG-out pocket requires the kinase activation loop to adopt a catalytically deficient conformation in which the ATP binding site becomes partially occluded by the Phe side chain of the DFG motif. While the DFG-out conformation is more favorable in the unphosphorylated kinase, phosphorylation of the activation loop shifts conformational equUibria to the more active DFG-in conformation, increases kinase activity, and often reduces the affinity of type 11 and type 111 inhibitors [1]. Although the search for chemical scaffolds which have affinity for the DFG-out pocket is moving to the forefront of kinase inhibitor research, efforts have been constrained by the lack of high-throughput assay technologies which can identify and discriminate for hgands which bind to and stabihze enzymatically inactive kinase conformation. 

Figure 2.3 First HTS for the detection allosteric Src inhibitors. In the absence of ligand, acrylodan-labeled cSrc shows two emission maxima at 475 and 505 nm. Type I ligands induce a robust loss of fluorescence intensity (arrows) at 475 nm, resulting in a red shift in the emission maxima to 510 nm (right panel). Type II and III inhibitors stabilize the inactive kinase conformation and elicit a different response in which the emissions at 475 and 505 nm are equally reduced. The emission signal at 445 nm is less sensitive to ligand binding and serves as an internal reference point, allowing for...

Simard, J.R., Grutter, C., Pawar, V., Aust, B., Wolf, A., Rabiller, M., Wulfert, S., Robubi, A., Milter, S., Ottmann, C., and Rauh, D. (2009) High-throughput screening to identify inhibitors which stabilize inactive kinase conformations in p38alpha. /. Am. Chem. Soc., 131 (51), 18478-18488. 

Simard JR, Grutter C, Pawar V et al. (2009) High-throughput screening to identify inhibitors which stabilize inactive kinase conformations in p38alpha. J Am Chem Soc 131 18478-18488... 

Simard JR, Getlik M, Grutter C, Schneider R, Wulfert S, Rauh D (2010) Fluorophore labeling of the glycine-rich loop as a method of identifying inhibitors that bind to active and inactive kinase conformations. J Am Chem Soc 132 4152-4160... 

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