User:Alice Harmon/Sandbox 4: Difference between revisions

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[[Image:ABA model 2 med.jpg|left]]

==Role in Abscisic Acid signaling==

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>PMID:12468729</ref><ref>PMID:12514244</ref><ref>PMID:19541597</ref><ref>PMID:17307925</ref>. As shown in the figure, in unstimulated cells SnRK2.6/OST1/SRK2E (K in the figure) and a protein phosphatase 2C (ABI1 or its homologs; P in the figure) are in a complex (K-P) in which the kinase is dephosphorylated and inactive<ref name ="Umezawa2009"> PMID:19805022 </ref><ref name ="Soon2013"> 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 ="Soon2013"/><ref>PMID:16365038</ref>. When ABA levels in the cytosol rise, ABA binds to an ABA receptor (PYR1/PYL/RCAR; R in the figure)<ref>PMID:19893533</ref><ref>PMID:19407143</ref><ref>PMID:~~19407143~~</ref>. The activated receptor (R.ABA) binds to the protein phosphatase (R.ABA-P) and inactivates it. SnRK2.6/OST1/SRK2E is still tethered to the phosphatase, but its active site 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~~>PMID: 19541597<~~/~~ref~~> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref~~>PMID: 17307925<~~/~~ref~~> in vegetative tissue and stress tolerance and growth regulation.

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 in the figure) and a protein phosphatase 2C (ABI1 or its homologs; P in the figure) are in a complex (K-P) in which the kinase is dephosphorylated and inactive<ref name ="Umezawa2009"> PMID:19805022 </ref><ref name ="Soon2013"> 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 ="Soon2013"/><ref>PMID:16365038</ref>. When ABA levels in the cytosol rise, ABA binds to an ABA receptor (PYR1/PYL/RCAR; R in the figure)<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 is still tethered to the phosphatase, but its active site 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.

Structures in the figure are: R, apo pYR2, [[3kdh]]; R.ABA, PYR2.ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R.ABA-P, PYR2.ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].

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==Kinase names and family members==

Two of SnRK2.6/OST1/SRK2E's three names originated from its membership in subclass III of the SnRK2 family of protein kinases. It was named SnRK2.6 by Hrabak et al.<ref>PMID:12805596</ref> and SRK2E by Umezawa et al.<ref~~>PMID: 19805022<~~/~~ref~~>. SnRK2 stands for SNF1-related kinase group 2, which in Arabidopsis has 10 members. SNRK2s are members of the calmodulin-dependent protein kinase clade of protein kinases. The third name OST1 (open stomata 1)<ref~~>12468729<~~/~~ref~~> is descriptive of the phenotype of plants bearing a gene mutation that produces an inactive protein kinase.

Two of SnRK2.6/OST1/SRK2E's three names originated from its membership in subclass III of the SnRK2 family of protein kinases. It was named SnRK2.6 by Hrabak et al.<ref>PMID:12805596</ref> and SRK2E by Umezawa et al.<ref name ="Umezawa2009"/>. SnRK2 stands for SNF1-related kinase group 2, which in Arabidopsis has 10 members. SNRK2s are members of the calmodulin-dependent protein kinase clade of protein kinases. The third name OST1 (open stomata 1)<ref name = "Mustilli2002"/> is descriptive of the phenotype of plants bearing a gene mutation that produces an inactive protein kinase.

Two other family members in Arabidopsis, SNRK2.2/SRK2D and SnRK2.3/SRK2I, are activated by the ABA pathway in the same manner as SnRK2.6. Each of these kinases interacts with a member of clade A of the protein phosphatase 2C family - ABI1, HAB1 or HAB2. In rice homologs of these protein kinases are named SAPK8, SAPK9 and SAPK10.

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==Kinase structure and regulation==

SnRK2.6/OST1/SRK2E has a primary structure comprising an amino terminal [[Eukaryotic Protein Kinase Catalytic Domain]] and a C-terminal sequence that contains the SNRK2 box, which is unique to the SNRK2 family and required for activity<ref>PMID: 16766677</ref>. Its C-terminus also contains a sequence called the ABA box, which is found only in the family members that are responsive to ABA<ref~~>PMID: 16766677</ref~~>. The latter sequence is required for binding to PP2C<ref~~>PMID: 16766677</ref~~>, but is not seen in the crystal structure (why??) (see below).

SnRK2.6/OST1/SRK2E has a primary structure comprising an amino terminal [[Eukaryotic Protein Kinase Catalytic Domain]] and a C-terminal sequence that contains the SNRK2 box, which is unique to the SNRK2 family and required for activity<ref name ="Belin2006"> PMID: 16766677</ref>. Its C-terminus also contains a sequence called the ABA box, which is found only in the family members that are responsive to ABA<ref name ="Belin2006">. The latter sequence is required for binding to PP2C<ref name ="Belin2006">, but is not seen in the crystal structure (why??) (see below).

{|

@@ Line 4: / Line 4: @@
 [[Image:ABA model 2 med.jpg|left]]
 ==Role in Abscisic Acid signaling==
-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>PMID:12468729</ref><ref>PMID:12514244</ref><ref>PMID:19541597</ref><ref>PMID:17307925</ref>. As shown in the figure, in unstimulated cells SnRK2.6/OST1/SRK2E (K in the figure) and a protein phosphatase 2C (ABI1 or its homologs; P in the figure) are in a complex (K-P) in which the kinase is dephosphorylated and inactive<ref name ="Umezawa2009"> PMID:19805022 </ref><ref name ="Soon2013"> 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 ="Soon2013"/><ref>PMID:16365038</ref>. When ABA levels in the cytosol rise,  ABA binds to an ABA receptor (PYR1/PYL/RCAR; R in the figure)<ref>PMID:19893533</ref><ref>PMID:19407143</ref><ref>PMID:19407143</ref>. The activated receptor (R<sup>.</sup>ABA) binds to the protein phosphatase (R<sup>.</sup>ABA-P) and inactivates it. SnRK2.6/OST1/SRK2E is still tethered to the phosphatase, but its active site 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>PMID: 19541597</ref> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref>PMID: 17307925</ref> in vegetative tissue and stress tolerance and growth regulation.
+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 in the figure) and a protein phosphatase 2C (ABI1 or its homologs; P in the figure) are in a complex (K-P) in which the kinase is dephosphorylated and inactive<ref name ="Umezawa2009"> PMID:19805022 </ref><ref name ="Soon2013"> 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 ="Soon2013"/><ref>PMID:16365038</ref>. When ABA levels in the cytosol rise,  ABA binds to an ABA receptor (PYR1/PYL/RCAR; R in the figure)<ref>PMID:19893533</ref><ref>PMID:19407143</ref><ref>PMID:19407142</ref>. The activated receptor (R<sup>.</sup>ABA) binds to the protein phosphatase (R<sup>.</sup>ABA-P) and inactivates it. SnRK2.6/OST1/SRK2E is still tethered to the phosphatase, but its active site 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.
 Structures in the figure are: R, apo pYR2, [[3kdh]];  R<sup>.</sup>ABA, PYR2<sup>.</sup>ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R<sup>.</sup>ABA-P, PYR2<sup>.</sup>ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].
@@ Line 10: / Line 10: @@
 ==Kinase names and family members==
-Two of SnRK2.6/OST1/SRK2E's three names originated from its membership in subclass III of the SnRK2 family of protein kinases. It was named SnRK2.6 by Hrabak et al.<ref>PMID:12805596</ref> and SRK2E by Umezawa et al.<ref>PMID: 19805022</ref>. SnRK2 stands for SNF1-related kinase group 2, which in Arabidopsis has 10 members. SNRK2s are members of the calmodulin-dependent protein kinase clade of protein kinases. The third name OST1 (open stomata 1)<ref>12468729</ref> is descriptive of the phenotype of plants bearing a gene mutation that produces an inactive protein kinase.
+Two of SnRK2.6/OST1/SRK2E's three names originated from its membership in subclass III of the SnRK2 family of protein kinases. It was named SnRK2.6 by Hrabak et al.<ref>PMID:12805596</ref> and SRK2E by Umezawa et al.<ref name ="Umezawa2009"/>. SnRK2 stands for SNF1-related kinase group 2, which in Arabidopsis has 10 members. SNRK2s are members of the calmodulin-dependent protein kinase clade of protein kinases. The third name OST1 (open stomata 1)<ref name = "Mustilli2002"/> is descriptive of the phenotype of plants bearing a gene mutation that produces an inactive protein kinase.
 Two other family members in Arabidopsis, SNRK2.2/SRK2D and SnRK2.3/SRK2I, are activated by the ABA pathway in the same manner as SnRK2.6. Each of these kinases interacts with a member of clade A of the protein phosphatase 2C family - ABI1, HAB1 or HAB2. In rice homologs of these protein kinases are named SAPK8, SAPK9 and SAPK10.
@@ Line 16: / Line 16: @@
 ==Kinase structure and regulation==
-SnRK2.6/OST1/SRK2E has a primary structure comprising an amino terminal [[Eukaryotic Protein Kinase Catalytic Domain]] and a C-terminal sequence that contains the SNRK2 box, which is unique to the SNRK2 family and required for activity<ref>PMID: 16766677</ref>. Its C-terminus also contains a sequence called the ABA box, which is found only in the family members that are responsive to ABA<ref>PMID: 16766677</ref>. The latter sequence is required for binding to PP2C<ref>PMID: 16766677</ref>, but is not seen in the crystal structure (why??) (see below).
+SnRK2.6/OST1/SRK2E has a primary structure comprising an amino terminal [[Eukaryotic Protein Kinase Catalytic Domain]] and a C-terminal sequence that contains the SNRK2 box, which is unique to the SNRK2 family and required for activity<ref name ="Belin2006"> PMID: 16766677</ref>. Its C-terminus also contains a sequence called the ABA box, which is found only in the family members that are responsive to ABA<ref name ="Belin2006">. The latter sequence is required for binding to PP2C<ref name ="Belin2006">, but is not seen in the crystal structure (why??) (see below).
+<ref name ="Soon2013"> PMID:22116026 </ref>
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