a, Activation of Ire1KR32 (3 μM) in the presence of different kinase inhibitors. b, Inhibitor structures, with probable hydrogen bonds shown by dashed lines. c, σA-weighted 3Fobs–2Fcalc map for APY29 bound to Ire1KR32Δ28 contoured at 1.5σ. d, The network of probable hydrogen bonds between APY29 and Ire1. e, The network of interactions between ADP•Mg and Ire1 (PDB ID 2RIO). f, Chelation of magnesium inhibits Ire1 RNase in the presence of ADP, but not of APY29. Error bars show variability between single-exponential fits from two independent measurements. Reactions contained 2 mM ADP or 100 μM APY29.