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Protein kinase C zeta type : ウィキペディア英語版 | Protein kinase C zeta type
Protein kinase C, zeta (PKCζ), also known as PRKCZ, is an enzyme that in humans is encoded by the ''PRKCZ'' gene. The PRKCZ gene encodes at least two alternative transcripts, the full-length PKCζ and an N-terminal truncated form PKMζ. PKMζ is thought to be responsible for maintaining long-term memories in the brain. The importance of PKCζ in the creation and maintenance of long-term potentiation was first described by Todd Sacktor and his colleagues at the State University of New York at Brooklyn in 1993. ==Structure== PKC-zeta has an N-terminal regulatory domain, followed by a hinge region and a C-terminal catalytic domain. Second messengers stimulate PKCs by binding to the regulatory domain, translocating the enzyme from cytosol to membrane, and producing a conformational change that removes auto-inhibition of the PKC catalytic protein kinase activity. PKM-zeta, a brain-specific isoform of PKC-zeta generated from an alternative transcript, lacks the regulatory region of full-length PKC-zeta and is therefore constitutively active. PKMζ is the independent catalytic domain of PKCζ and, lacking an autoinhibitory regulatory domain of the full-length PKCζ, is constitutively and persistently active, without the need of a second messenger. It was originally thought of as being a cleavage product of full-length PKCζ, an atypical isoform of protein kinase C (PKC). Like other PKC isoforms, PKCζ is a serine/threonine kinase that adds phosphate groups to target proteins. It is atypical in that unlike other PKC isoforms, PKCζ does not require calcium or diacylglycerol (DAG) to become active, but rather relies on a different second messenger, presumably generated through a phosphoinositide 3-kinase (PI3-kinase) pathway. It is now known that PKMζ is not the result of cleavage of full-length PKCζ, but rather, in the mammalian brain, is translated from its own brain-specific mRNA, that is transcribed by an internal promoter within the PKCζ gene.〔 The promoter for full-length PKCζ is largely inactive in the forebrain and so PKMζ is the dominant form of ζ in the forebrain and the only PKM that is translated from its own mRNA.
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