second protein kinase C conserved region 1 (C1 domain) found in novel protein kinase C (nPKC) epsilon, eta, 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 domain. nPKCs are calcium-independent, but require DAG (1,2-diacylglycerol) and phosphatidylserine (PS) for activity. PKC-epsilon has been shown to behave as an oncoprotein. Its overexpression contributes to neoplastic transformation depending on the cell type. It contributes to oncogenesis by inducing disordered cell growth and inhibiting cell death. It also plays a role in tumor invasion and metastasis. PKC-epsilon has also been found to confer cardioprotection against ischemia and reperfusion-mediated damage. Other cellular functions include the regulation of gene expression, cell adhesion, and cell motility. PKC-eta is predominantly expressed in squamous epithelia, where it plays a crucial role in the signaling of cell-type specific differentiation. It is also expressed in pro-B cells and early-stage thymocytes, and acts as a key regulator in early B-cell development. PKC-eta increases glioblastoma multiforme (GBM) proliferation and resistance to radiation, and is being developed as a therapeutic target for the management of GBM. Members of this family contain two copies of C1 domain. This model corresponds to the second 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.