Catalytic domain of the Serine/Threonine Kinase, Novel Protein Kinase C eta
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. 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. 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. The nPKC-eta subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.