PMID: 23289588

Authors:

Rahman GM, Shanker S, Lewin NE, Kedei N, Hill CS, Prasad BV, Blumberg P, Das J

Title:

Identification of the Activator Binding Residues in the Second Cysteine-Rich Regulatory Domain of Protein Kinase C Theta.

Journal:

Biochem J. 2013 Jan 4.

Abstract:

PKCtheta is predominantly expressed in T-cells and critically involved in immunity. Design of PKCtheta selective molecules to manage autoimmune disorders by targeting its activator binding C1 domain requires the knowledge of its structure and the activator binding residues. The C1 domain consists of twin C1 domains, C1A and C1B, of which C1B plays the critical role in the membrane translocation and activation of PKCq. Here, we determined the crystal structure of the PKCthetaC1B to 1.63A resolution, which showed that the Trp-253 at the rim of the activator binding pocket was oriented towards the membrane whereas in PKCdC1B, the homologous tryptophan was oriented away from the membrane. This particular orientation of Trp-253 abolishes the possible p-stacking interactions between Trp-253 and His-270 and the cation-p interactions between Trp-253 and Arg-272, which are present between the homologous residues in PKCdC1B. To further probe the structural constraints on activator binding, five residues lining the activator binding site were mutated (Y239A, T243A, W253G, L255G and Q258G) and the binding affinities of the PKCthetaC1B mutants were measured. These mutants showed reduced binding affinities for phorbol ester (PDBu) and diacylglycerol (DOG). All the five full length PKCtheta mutants exhibited reduced phorbol ester-induced membrane translocation compared to the wild type. These results provide insights into the PKCq activator binding domain, which will aid in future design of PKCtheta selective molecules.