Linking RNase activity and high-order oligomerization of Ire1 kinase/RNase. (a) Cooperative activation of Ire1 RNase with and without 2 mmol ADP Mg . The dashed line marks the standard assay condition at 3 μmol Ire1KR32. (b) Opacity at 500 nm versus concentration of Ire1KR32 with and without 2 mmol ADP Mg. (c) RNase activation profiles for Ire1KR32, Ire1KR32(D797N, K799N) bearing a catalytically disabled, unphosphorylated kinase domain, and for Ire1KR32(E715K). Reactions were conducted as in (a) in the presence of 2 mmol ADP Mg. (d) OD500 response versus concentration of Ire1KR32, Ire1KR32(D797N, K799N) and Ire1KR32(E715K). Assays were conducted as in (b) in the presence of 2 mmol ADP Mg.