User:Alice Harmon/Sandbox 4: Difference between revisions

SnRK2.6/OST1/SRK2E is a triply-named protein kinase from Arabidopsis, which is activated by the abscisic acid (ABA) response pathway in plants<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>. As shown in the figure, in unstimulated cells SnRK2.6/OST1/SRK2E (K) and a protein phosphatase 2C (P) are in a complex (K-P) in which the kinase is dephosphorylated and inactive<ref name ="Umezawa2009"> PMID:19805022 </ref><ref name ="Soon2012"> PMID:22116026 </ref>. The kinase and phosphatase are proposed to be tethered via the C-terminal sequence (dashed line) of the kinase<ref name ="Umezawa2009"/><ref name ="Soon2012"/><ref>PMID:16365038</ref>. When ABA levels in the cytosol rise,  ABA binds to an ABA receptor (R)<ref>PMID:19893533</ref><ref>PMID:19407143</ref><ref>PMID:19407142</ref>. The activated receptor (R^.ABA) binds to the protein phosphatase (R^.ABA-P) and inactivates it. SnRK2.6/OST1/SRK2E, although still tethered to the phosphatase, is now free to be activated by autophosphorylation or phoshorylation by another protein kinase<ref>PMID:17103012</ref><ref>PMID:16980311</ref>.  Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID: 19785574</ref> in guard cells and stomatal closure; 2)  transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.  

===PP2C structures===