Structure of the Catalytic Domain of Human Protein Kinase C βII Complexed with a Bisindolylmaleimide Inhibitor.

The conventional protein kinase C isoform, PKCβII, is a signaling kinase activated during the hyperglycemic state and has been associated with the development of microvascular abnormalities associated with diabetes. PKCflII, therefore, has been identified as a therapeutic target where inhibitors of its kinase activity are being pursued for treatment of microvascular-related diabetic complications. In this report, we describe the crystal structure of the catalytic domain of PKCβII complexed with an inhibitor at 2.6 Å resolution. The kinase domain of PKCβII was cleaved and purified from full-length PKCβII expressed in baculovirus-infected insect cells. The overall kinase domain structure follows the classical bilobal fold and is in its fully activated conformation with three well-defined phosphorylated residues: Thr-500, Thr-641, and Ser-660. Different from the crystal structures of nonconventional PKC isoforms, the C-terminus of the PKCβII catalytic domain is almost fully ordered and features a novel α helix in the turn motif. An ATP-competitive inhibitor, 2-methyl-1H-indol-3-yl-BIM-1, was crystallized with the PKCβII catalytic domain as a dimer of two enzyme-inhibitor complexes. The bound inhibitor adopts a nonplanar conformation in the ATP-binding site, with the kinase domain taking on an intermediate, open conformation. This PKCβII-inhibitor complex represents the first structural description of any conventional PKC kinase domain. Given the pathogenic role of PKCβII in the development of diabetic complications, this structure can serve as a template for the rational design of inhibitors as potential therapeutic agents. [ABSTRACT FROM AUTHOR]