Structure of human protein kinase C eta (PKCη) C2 domain and identification of phosphorylation sites

Protein kinase C eta (PKCη) is one of several PKC isoforms found in humans. It is a novel PKC isoform in that it is activated by diacylglycerol and anionic phospholipids but not calcium. The crystal structure of the PKCη-C2 domain, which is thought to mediate anionic phospholipid sensing in the protein, was determined at 1.75 Å resolution. The structure is similar to that of the PKC epsilon C2 domain but with significant variations at the putative lipid-binding site. Two serine residues within PKC eta were identified in vitro as potential autophosphorylation sites. In the unphosphorylated structure both serines line the putative lipid-binding site and may therefore play a role in the lipid-regulation of the kinase.