Sandbox Reserved 935: Difference between revisions

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<scene name='57/579705/4oab/12'>Testi3</scene>

==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. Both activation of the kinase domain and activation of the P-ATPase 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 />.

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-ATPase 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 Tyrosine-872 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).

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In this structure, the adenine and ribose parts of ADP are well ordered, whereas the diphosphate is more flexible <ref name=Bojar2014 />. There are hydrogen-bonding interactions of the adenine base and ribose with the BRI1 hinge region main chain atoms (Glutamate-957, Methionine-959) and with two water molecules. When it was an ATP, the catalytic Aspartate-1009 caused it to γ -phosphate to face outwards. BRI<sup>865-1196</sup> can efficiently hydrolyse ATP to ADP and to a lesser extent GTP to GDP.

There is a balance between phosphorylation dependent activation and several potential mechanisms for deactivation of BRI1 <ref name=Oh2012>Man-Ho Oh, Xiaofeng Wang, Steven D. Clouse and Steven C. Huber: Deactivation of the Arabidopsis Brassinosteroid Insensitive 1(BRI1) receptor kinase by autophosphorylation within the glycine-rich loop. PNAS, January 3, 2012; vol. 109, no. 1, 327–332. Doi: 10.1073/pnas.1108321109</ref>. One of them involves autophosphorylation of serine891 in the ATP binding domain, which is involved in the binding and positioning of ATP. The phosphorylation of this residue reduces, but doesn't completely inhibit, the activity of the kinase domain. When this serine is mutated into aspartate or glutamate (which are residues with negative charge and probably function as phosphomimetics), it results into dwarfed ~~arabidopsis~~ plants. Phosphorylation of Serine-891 also reduces autophosphorylation on several other residues that are phosphorylated after brassinosteroid induced activation. The deactivation associated with serine891 phosphorylation seems to play a role in attenuation of signaling rather than maintaining the inactive state of BRI1 in the absence of its hormone ligand.

There is a balance between phosphorylation dependent activation and several potential mechanisms for deactivation of BRI1 <ref name=Oh2012>Man-Ho Oh, Xiaofeng Wang, Steven D. Clouse and Steven C. Huber: Deactivation of the ''Arabidopsis'' Brassinosteroid Insensitive 1(BRI1) receptor kinase by autophosphorylation within the glycine-rich loop. PNAS, January 3, 2012; vol. 109, no. 1, 327–332. Doi: 10.1073/pnas.1108321109</ref>. One of them involves autophosphorylation of serine891 in the ATP binding domain, which is involved in the binding and positioning of ATP. The phosphorylation of this residue reduces, but doesn't completely inhibit, the activity of the kinase domain. When this serine is mutated into aspartate or glutamate (which are residues with negative charge and probably function as phosphomimetics), it results into dwarfed ''Arabidopsis'' plants. Phosphorylation of Serine-891 also reduces autophosphorylation on several other residues that are phosphorylated after brassinosteroid induced activation. The deactivation associated with serine891 phosphorylation seems to play a role in attenuation of signaling rather than maintaining the inactive state of BRI1 in the absence of its hormone ligand.

Threonine-872 in the juxtamembrane domain is another phosphorylation site <ref name=Oh2012 />. Its phosphorylation may inhibit the kinase activity and follows soon after the the brassinosteroid activation of the domain. Tyrosine831 in the juxtamembrane domain is not essential for the activity of the kinase doamain, but it does have a regulatory role <ref name=Oh2009>Man-Ho Oh, Steven D. Clouse and Steven C. Huber: Tyrosine phosphorylation in brassinosteroid signaling. Plant Signaling & Behavior 4:12, 1182-1185; December 2009. PMID: 20514242</ref>. Its phosphorylation causes inhibition of plant growth and delay of flowering. On the other hand, tyrosine956 in the kinase domain is important for kinase activity and its phosphorylation is believed to have an inhibitory role.

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@@ Line 19: / Line 19: @@
 <scene name='57/579705/4oab/12'>Testi3</scene>
 ==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. Both activation of the kinase domain and activation of the P-ATPase 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 />.
+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-ATPase 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 Tyrosine-872 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).
@@ Line 35: / Line 35: @@
 In this structure, the adenine and ribose parts of ADP are well ordered, whereas the diphosphate is more flexible <ref name=Bojar2014 />. There are hydrogen-bonding interactions of the adenine base and ribose with the BRI1 hinge region main chain atoms (Glutamate-957, Methionine-959) and with two water molecules. When it was an ATP, the catalytic Aspartate-1009 caused it to γ -phosphate to face outwards. BRI<sup>865-1196</sup> can efficiently hydrolyse ATP to ADP and to a lesser extent GTP to GDP.
-There is a balance between phosphorylation dependent activation and several potential mechanisms for deactivation of BRI1 <ref name=Oh2012>Man-Ho Oh, Xiaofeng Wang, Steven D. Clouse and Steven C. Huber: Deactivation of the Arabidopsis Brassinosteroid Insensitive 1(BRI1) receptor kinase by autophosphorylation within the glycine-rich loop. PNAS, January 3, 2012; vol. 109, no. 1, 327–332. Doi: 10.1073/pnas.1108321109</ref>. One of them involves autophosphorylation of serine891 in the ATP binding domain, which is involved in the binding and positioning of ATP. The phosphorylation of this residue reduces, but doesn't completely inhibit, the activity of the kinase domain. When this serine is mutated into aspartate or glutamate (which are residues with negative charge and probably function as phosphomimetics), it results into dwarfed arabidopsis plants. Phosphorylation of Serine-891 also reduces autophosphorylation on several other residues that are phosphorylated after brassinosteroid induced activation. The deactivation associated with serine891 phosphorylation seems to play a role in attenuation of signaling rather than maintaining the inactive state of BRI1 in the absence of its hormone ligand.
+There is a balance between phosphorylation dependent activation and several potential mechanisms for deactivation of BRI1 <ref name=Oh2012>Man-Ho Oh, Xiaofeng Wang, Steven D. Clouse and Steven C. Huber: Deactivation of the ''Arabidopsis'' Brassinosteroid Insensitive 1(BRI1) receptor kinase by autophosphorylation within the glycine-rich loop. PNAS, January 3, 2012; vol. 109, no. 1, 327–332. Doi: 10.1073/pnas.1108321109</ref>. One of them involves autophosphorylation of serine891 in the ATP binding domain, which is involved in the binding and positioning of ATP. The phosphorylation of this residue reduces, but doesn't completely inhibit, the activity of the kinase domain. When this serine is mutated into aspartate or glutamate (which are residues with negative charge and probably function as phosphomimetics), it results into dwarfed ''Arabidopsis'' plants. Phosphorylation of Serine-891 also reduces autophosphorylation on several other residues that are phosphorylated after brassinosteroid induced activation. The deactivation associated with serine891 phosphorylation seems to play a role in attenuation of signaling rather than maintaining the inactive state of BRI1 in the absence of its hormone ligand.
 Threonine-872 in the juxtamembrane domain is another phosphorylation site <ref name=Oh2012 />. Its phosphorylation may inhibit the kinase activity and follows soon after the the brassinosteroid activation of the domain. Tyrosine831 in the juxtamembrane domain is not essential for the activity of the kinase doamain, but it does have a regulatory role <ref name=Oh2009>Man-Ho Oh, Steven D. Clouse and Steven C. Huber: Tyrosine phosphorylation in brassinosteroid signaling. Plant Signaling & Behavior 4:12, 1182-1185; December 2009. PMID: 20514242</ref>. Its phosphorylation causes inhibition of plant growth and delay of flowering. On the other hand, tyrosine956 in the kinase domain is important for kinase activity and its phosphorylation is believed to have an inhibitory role.