Catalytic domain of the Serine/Threonine kinase, Plant SNT7
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. SNT7 is a plant thylakoid-associated kinase that is essential in short- and long-term acclimation responses to cope with various light conditions in order to maintain photosynthetic redox poise for optimal photosynthetic performance. Short-term response involves state transitions over periods of minutes while the long-term response (LTR) occurs over hours to days and involves changing the relative amounts of photosystems I and II. SNT7 acts as a redox sensor and a signal transducer for both responses, which are triggered by the redox state of the plastoquinone (PQ) pool. It is positioned at the top of a phosphorylation cascade that induces state transitions by phosphorylating light-harvesting complex II (LHCII), and triggers the LTR through the phosphorylation of chloroplast proteins. The SNT7 subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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