Sandbox Reserved 935: Difference between revisions
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BRI1 is a dual-specificity kinase: it can both autophosphorylate on tyrosine residues in the kinase and juxtamembrabe domains (residues 814-865, part of which is not in this model) and also transphosphorylate tyrosine residues in other proteins <ref name=Bojar2014 />. The juxtamembrane domain is important for the kinase domain activity. | BRI1 is a dual-specificity kinase: it can both autophosphorylate on tyrosine residues in the kinase and juxtamembrabe domains (residues 814-865, part of which is not in this model) and also transphosphorylate tyrosine residues in other proteins <ref name=Bojar2014 />. The juxtamembrane domain is important for the kinase domain activity. | ||
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 ( | 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. | ||
