first protein kinase C conserved region 1 (C1 domain) found in classical (or conventional) protein kinase C (cPKC), novel protein kinase C (nPKC), and similar proteins
PKCs are classified into three groups (classical, atypical, and novel) depending on their mode of activation and the structural characteristics of their regulatory domains. PKCs undergo three phosphorylations in order to take mature forms. In addition, cPKCs depend on calcium, DAG (1,2-diacylglycerol), and in most cases, phosphatidylserine (PS) for activation. nPKCs are calcium-independent, but require DAG and PS for activity, while atypical PKCs (aPKCs) only require PS. PKCs phosphorylate and modify the activities of a wide variety of cellular proteins including receptors, enzymes, cytoskeletal proteins, transcription factors, and other kinases. They play a central role in signal transduction pathways that regulate cell migration and polarity, proliferation, differentiation, and apoptosis. This family includes classical PKCs (cPKCs) and novel PKCs (nPKCs). There are four cPKC isoforms (named alpha, betaI, betaII, and gamma) and four nPKC isoforms (delta, epsilon, eta, and theta). Members of this family contain two copies of the C1 domain. This model corresponds to the first one. The C1 domain is a cysteine-rich zinc binding domain that does not bind DNA nor possess structural similarity to conventional zinc finger domains; it contains two separate Zn(2+)-binding sites.