Abstract: The present invention relates to a kinase labelled at an amino acid naturally present or introduced in the P-loop of said kinase, wherein said labelling is effected at a free thiol or amino group of said amino acid and said label is (a) a thiol- or amino-reactive fluorophore sensitive to polarity changes in its environment; or (b) a thiol-reactive spin label, an isotope or an isotope-enriched thiol- or amino-reactive label, such that said fluorophore, spin label, isotope or isotope-enriched label does not inhibit the catalytic activity and does not interfere with the stability of the kinase. The invention furthermore relates to a method of screening for kinase inhibitors, a method of determining the kinetics of ligand binding and/or of dissociation of a kinase inhibitor and a method of generating mutated kinases suitable for the screening of kinase inhibitors using the kinase of the present invention.

Abstract: The present invention relates to a kinase labeled at an amino acid having a free thiol or amino group, wherein said amino acid is naturally present or introduced in the activation loop of said kinase, with (a) a thiol- or amino-reactive fluorophore sensitive to polarity changes in its environment; or (b) a thiol-reactive spin label, an isotope or an isotope-enriched thiol- or amino-reactive label, such that said fluorophore, spin label, isotope or isotope-enriched label does not inhibit the catalytic activity and does not interfere with the stability of the kinase. The invention furthermore relates to a method of screening for kinase inhibitor, a method of determining the kinetics of ligand binding and/or of dissociation of a kinase inhibitor and a method of generating mutated kinases suitable for the screening of kinase inhibitors using the kinase of the present invention.