PP1 Analog II, 1NM-PP1 is a cell-permeable PP1 analog that acts as a potent and selective inhibitor of mutant kinases over their wild-type progenitors. 1-NM-PP1 is a cell permeable inhibitor of kinases that have been mutated, by a single base substitution, to become ‘analog sensitive', as compared to the wild-type kinase. 1-NM-PP1 was first developed to optimally inhibit v-Src-as1, with an I338G substitution, preferentially over v-Src (IC50 = 4.2 nM versus 28 μM, respectively). The homologous mutation in other kinases generated similar analog sensitivity (e.g., IC50 = 3.2 nM for c-Fyn-as1 versus 1.0 μM for c-Fyn; 5.0 nM for CDK2-as1 versus 29 μM for CDK2; 8.0 nM for CAMKII-as1 versus 24 μM for CAMKII). This approach has been used to elucidate functions of several kinases in both mammalian and yeast systems. In addition it has been shown to activate mutants of Ire1, a transmembrane kinase.