Figure 1.

Classification and structural characteristics of PKC isoforms. Although the catalytic domain of PKC is conserved, the three subgroups have different regulatory domains. The classical PKC isoforms (cPKC) share all typical regulatory features: the autoinhibitory pseudosubstrate motif, two DAG-binding C1 domains and the calcium-binding C2 domain. Novel PKC isoforms (nPKC) lack a calcium-binding motif but contain an extended N-terminal domain that can receive regulatory signals, and they are still being regulated by DAG. On the other hand, the catalytic activity of atypical PKC isoforms (aPKC) is independent of DAG and calcium.