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Two-component regulatory system : ウィキペディア英語版 | Two-component regulatory system
In the field of molecular biology, a two-component regulatory system serves as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions. They typically consist of a membrane-bound histidine kinase that senses a specific environmental stimulus and a corresponding response regulator that mediates the cellular response, mostly through differential expression of target genes. Two component signaling systems are widely occurring in prokaryotes whereas only a few two-component systems have been identified in eukaryotic organisms.〔 == Mechanism of action ==
Signal transduction occurs through the transfer of phosphoryl groups from adenosine triphosphate (ATP) to a specific histidine residue in the histidine kinases (HK). This is an autophosphorylation reaction. The response regulators (RRs) were shown to be phosphorylated on an aspartate residue and to be protein phosphatases for the histidine kinases.〔http://www.jbc.org/content/264/36/21770.full.pdf〕 The response regulators are therefore enzymes with a covalent intermediate that alters response-regulator output function.〔http://www.ncbi.nlm.nih.gov/pmc/articles/PMC206329/〕 Phosphorylation causes the response regulator's conformation to change, usually activating an attached output domain, which then leads to the stimulation (or repression) of expression of target genes. The level of phosphorylation of the response regulator controls its activity. Some HK are bifunctional, catalysing both the phosphorylation and dephosphorylation of their cognate RR. The input stimuli can regulate either the kinase or phosphatase activity of the bifunctional HK.
抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Two-component regulatory system」の詳細全文を読む
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