Sandbox Reserved 935: Difference between revisions
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<scene name='57/579705/4oab/12'>Testi3</scene> | <scene name='57/579705/4oab/12'>Testi3</scene> | ||
==Introduction== | ==Introduction== | ||
Brassinosteroid insensitive 1 (BRI1) is a membrane receptor that senses brassinosteroides, which are polyhydroxylated steroid hormones <ref name=Bojar2014>Daniel Bojar, Jacobo Martinez, Julia Santiago, Vladimir Rybin, Richard Bayliss and Michael Hothorn: Crystal structures of the phosphorylated BRI1 kinase domain and implications for brassinosteroid signal initiation. The Plant Journal (2014) 78, 31–43. PMID: 24461462 doi: 10.1111/tpj.12445</ref>. Brassinosteroids control planth growth and development by activating BRI1 and starting a signaling pathway that leads to nuclear thanscription factors being activated. They do so by inducing rapid plant cell wall expansion and hyperpolarization <ref name=”Witthöft2011">Janika Witthöft, Katharina Caesar, Kirstin Elgass, Peter Huppenberger, Joachim Kilian, Frank Schleifenbaum, Claudia Oecking and Klaus Harter: The activation of the Arabidopsis P-ATPase 1 by the brassinosteroid receptor BRI1 is independent of threonine 948 phosphorylation. Plant Signaling & Behavior 6:7, 1063-1066; July 2011. DOI: 10.4161/psb.6.7.15650</ref>. The brassinosteroid induced association of BRI1 with the proton pump of P-type H+-ATPase also seems to be necessary for the activation of P-ATPase in the plasma membrane, though it is not currently known if it’s by serine/threonine phosphorylation or some other protein-protein interaction. BRI1 is thought to be a dual-specificity kinase and it has structural features reminiscent of both serine/threonine and tyrosine kinases <ref name=Bojar2014 />. | Brassinosteroid insensitive 1 (BRI1) is a membrane receptor that senses brassinosteroides, which are polyhydroxylated steroid hormones <ref name=Bojar2014>Daniel Bojar, Jacobo Martinez, Julia Santiago, Vladimir Rybin, Richard Bayliss and Michael Hothorn: Crystal structures of the phosphorylated BRI1 kinase domain and implications for brassinosteroid signal initiation. The Plant Journal (2014) 78, 31–43. PMID: 24461462 doi: 10.1111/tpj.12445</ref>. Brassinosteroids control planth growth and development by activating BRI1 and starting a signaling pathway that leads to nuclear thanscription factors being activated. They do so by inducing rapid plant cell wall expansion and hyperpolarization <ref name=”Witthöft2011">Janika Witthöft, Katharina Caesar, Kirstin Elgass, Peter Huppenberger, Joachim Kilian, Frank Schleifenbaum, Claudia Oecking and Klaus Harter: The activation of the Arabidopsis P-ATPase 1 by the brassinosteroid receptor BRI1 is independent of threonine 948 phosphorylation. Plant Signaling & Behavior 6:7, 1063-1066; July 2011. DOI: 10.4161/psb.6.7.15650</ref>. The brassinosteroid induced association of BRI1 with the proton pump of P-type H+-ATPase also seems to be necessary for the activation of P-ATPase in the plasma membrane, though it is not currently known if it’s by serine/threonine phosphorylation or some other protein-protein interaction. Both activation of the kinase domain and activation of the P-ATPas are necessary for the induction of the hyperpolarization and cell-wall expansion and brassinolides affect the interaction between them <ref name=Caesar2011>Katharina Caesar, Kirstin Elgass, Zhonghua Chen, Peter Huppenberger, Janika Witthöft, Frank Schleifenbaum, Michael R. Blatt, Claudia Oecking and Klaus Harter: A fast brassinolide-regulated response pathway in the plasma membrane of Arabidopsis thaliana. The Plant Journal (2011) 66, 528–540. doi: 10.1111/j.1365-313X.2011.04510.x</ref>. BRI1 is thought to be a dual-specificity kinase and it has structural features reminiscent of both serine/threonine and tyrosine kinases <ref name=Bojar2014 />. | ||
In the cell, BRI1 cycles between the plasma membrane and endosomes <ref name=Bojar2014 />. When not activated, BRI1 is auto-inhibited by its own C-terminal tail as well as auto-phosphorylation of Thr872 and interaction with BRI1 kinase inhibitor protein BKI1 in the kinase domain. BKI1 also contains an N-terminal targeting motif for the plasma membrane. When the extracellular LRR domain gets activated by a brassinosteroid, it causes a reordering of 70 residues and creates a docking platform for the co-receptor SERK (somatic embryogenesis receptor kinase). The C-termini of BRI1 and SERK trans-phosphorylate each other, releasing the BKI1 from BRI1 and allowing BRI1 to phosphorylate immediate downstream signaling components (such as BRI1 substrate kinases, or BSKs). | In the cell, BRI1 cycles between the plasma membrane and endosomes <ref name=Bojar2014 />. When not activated, BRI1 is auto-inhibited by its own C-terminal tail as well as auto-phosphorylation of Thr872 and interaction with BRI1 kinase inhibitor protein BKI1 in the kinase domain. BKI1 also contains an N-terminal targeting motif for the plasma membrane. When the extracellular LRR domain gets activated by a brassinosteroid, it causes a reordering of 70 residues and creates a docking platform for the co-receptor SERK (somatic embryogenesis receptor kinase). The C-termini of BRI1 and SERK trans-phosphorylate each other, releasing the BKI1 from BRI1 and allowing BRI1 to phosphorylate immediate downstream signaling components (such as BRI1 substrate kinases, or BSKs). | ||
