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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 Tyrosine872 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 this article we will concentrate on the BRI1 kinase domain and its interaction with the nucleotides ATP/ADP.

Sandbox Reserved 935: Difference between revisions

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 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 Tyrosine872 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 this article we will concentrate on the BRI1 kinase domain and its interaction with the nucleotides ATP/ADP.