User:Alice Harmon/Sandbox 4: Difference between revisions
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[[Image:ABA model small.jpg|left]] | [[Image:ABA model small.jpg|left]] | ||
==Role in | ==Role in Abscisic Acid signaling== | ||
SnRK2.6/OST1/SRK2E is a triply-named protein kinase from Arabidopsis, which, along with its homologs, is activated by the abscisic acid (ABA) response pathway in plants. 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. When ABA levels in the cytosol rise, ABA binds to an ABA receptor (PYR1/PYL/RCAR; R in the figure). The activated receptor (R<sup>.</sup>ABA) steals the protein phosphatase from its complex with SnRK2.6/OST1/SRK2E and forms its own complex with the phosphatase (R<sup>.</sup>ABA-P). SnRK2.6/OST1/SRK2E is now free to be activated by autophosphorylation or phoshorylation by another protein kinase. Activation of this pathway by ABA leads to phosphorylation by SnRK2.6/OST1/SRK2E 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, along with its homologs, is activated by the abscisic acid (ABA) response pathway in plants. 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. When ABA levels in the cytosol rise, ABA binds to an ABA receptor (PYR1/PYL/RCAR; R in the figure). The activated receptor (R<sup>.</sup>ABA) steals the protein phosphatase from its complex with SnRK2.6/OST1/SRK2E and forms its own complex with the phosphatase (R<sup>.</sup>ABA-P). SnRK2.6/OST1/SRK2E is now free to be activated by autophosphorylation or phoshorylation by another protein kinase. Activation of this pathway by ABA leads to phosphorylation by SnRK2.6/OST1/SRK2E 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. | ||
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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>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). | ||
The structure | {| | ||
|'''Left scene''' - The crystal structure [[3uc4]] shows that SnRK2.6 has a typical catalytic domain (see [[Eukaryotic Protein Kinase Catalytic Domain]]) except for an additional α-helix in the small lobe that is formed by SNRK2 box sequence. This helix parallels subdomain III and resembles **blah blah** kinase structures. | |||
<scene name='55/559985/Aposnrk2_6critical/1'>Important structures</scene> | <br> | ||
Activation loop (with gap) in blue<br> | |'''Right scene''' - The crystal structure [[3ujg]] shows | ||
|- | |||
| <applet load='3ujg' size='400' frame='true' align='left' caption='3uc4 - Apo SnRK2.6' scene = '55/559985/Aposnrk2_6/3' /><br clear='both'>'''3uc4 scenes''' <Br><scene name='55/559985/Aposnrk2_6/3'>1. Default scene</scene><Br><scene name='55/559985/Aposnrk2_6critical/1'>2. Important structures</scene>Activation loop (with gap) in blue<br> | |||
Catalytic loop in orchid<br> | Catalytic loop in orchid<br> | ||
C-helix in yellow<br> | C-helix in yellow<br> | ||
K in chartreuse<br> | K in chartreuse<br> | ||
Snrk2 box (unique to Snrk's) in turquoise.<br> | Snrk2 box (unique to Snrk's) in turquoise.<br> | ||
C-terminal acidic domain missing. | C-terminal acidic domain missing.<br><br><br> | ||
| <applet load='3ujg' size='400' frame='true' align='left' caption='3hx4 - active TgCDPK1' scene = '55/559985/Aposnrk2_6/2' /><Br clear='both'>'''3ujg scenes'''<Br><scene name='55/559985/Aposnrk2_6/2'>1. Default Scene</scene>The SnRK2.6–HAB1 complex was constructed as a fusion protein with a H6-tag (MAHHHHHHA) at the N-terminus of SnRK2.6 (residues 11–362) fused to HAB1(172–511) with a GSGSAGSAAGS linker. D296A and E297A surface entropy reduction mutation sites. <Br><scene name='55/559985/Ost1hab1_interaction/1'>2. Zone of interaction </scene><br> | |||
kinase activation loop in blue<br> | |||
phosphatase W385 in brown | |||
|} | |||
ABA box is not seen in the crystal structure. | ABA box is not seen in the crystal structure. | ||
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Clearest picture of Pyr1 gate - latch is in Annu Reviews article | Clearest picture of Pyr1 gate - latch is in Annu Reviews article | ||
unused: <scene name='55/559985/Aposnrk2_6/4'>Cysteines in transparent kinase</scene><br> | unused: <scene name='55/559985/Aposnrk2_6/4'>Cysteines in transparent kinase</scene><br> | ||
Revision as of 20:04, 28 September 2013
SnRK2.6/OST1/SRK2ESnRK2.6/OST1/SRK2E
Role in Abscisic Acid signalingRole in Abscisic Acid signaling
SnRK2.6/OST1/SRK2E is a triply-named protein kinase from Arabidopsis, which, along with its homologs, is activated by the abscisic acid (ABA) response pathway in plants. 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. When ABA levels in the cytosol rise, ABA binds to an ABA receptor (PYR1/PYL/RCAR; R in the figure). The activated receptor (R.ABA) steals the protein phosphatase from its complex with SnRK2.6/OST1/SRK2E and forms its own complex with the phosphatase (R.ABA-P). SnRK2.6/OST1/SRK2E is now free to be activated by autophosphorylation or phoshorylation by another protein kinase. Activation of this pathway by ABA leads to phosphorylation by SnRK2.6/OST1/SRK2E of: 1) ion channels SLAC1[1] and KAT1[2] in guard cells and stomatal closure; 2) transcription factor ABI5[3] in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF [4][5] 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.
Kinase names and family membersKinase 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.[6] and SRK2E by Umezawa et al.[7]. 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)[8] 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.
Kinase structure and regulationKinase 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[9]. Its C-terminus also contains a sequence called the ABA box, which is found only in the family members that are responsive to ABA[10]. The latter sequence is required for binding to PP2C[11], but is not seen in the crystal structure (why??) (see below).
| Left scene - The crystal structure 3uc4 shows that SnRK2.6 has a typical catalytic domain (see Eukaryotic Protein Kinase Catalytic Domain) except for an additional α-helix in the small lobe that is formed by SNRK2 box sequence. This helix parallels subdomain III and resembles **blah blah** kinase structures.
|
Right scene - The crystal structure 3ujg shows | ||||||||||||
3uc4 scenes Activation loop (with gap) in blue Catalytic loop in orchid |
3ujg scenes The SnRK2.6–HAB1 complex was constructed as a fusion protein with a H6-tag (MAHHHHHHA) at the N-terminus of SnRK2.6 (residues 11–362) fused to HAB1(172–511) with a GSGSAGSAAGS linker. D296A and E297A surface entropy reduction mutation sites. kinase activation loop in blue |
ABA box is not seen in the crystal structure.
Clearest picture of Pyr1 gate - latch is in Annu Reviews article
unused:
SNRK2 structuresSNRK2 structures
3uc3 Arabidopsis thaliana SNRK2.3 + Co2+
3zut AtSNRK2.6 (D160A mutant)+ ANP
3zuu AtSNRK2.6 (D160A, S175D mutant) + gold
3uc4 apoAtSNRK2.6 (D59A, E60A mutant)
3udb apoAtSNRK2.6 (C131A, C157A, C159A, S7A, s29A, s43A, S166A, T175A)
complex with a protein phosphatase 2C
3ujg AtSNRK2.6 (D296A) + HAB1 + Mg2+
PP2C structuresPP2C structures
1a6q – hPP2C
2iq1 – hPP2C κ
2p8e – hPP2C β
2cm1 – PP2C + Mn – Micobacterium tuberculosis
3d8k – PP2C – Toxoplasma gondii
3jrq, 3kdj, 3nmn – AtPP2C + Pyl1 – Arabidopsis thaliana
3nmt, 3kb3, 3nmv, 3ujl – AtPP2C + Pyl2
4ds8 – AtPP2C + Pyl3 + Mn
3rt0 – AtPP2C (mutant) + Pyl10
3qn1, 3zvu – AtPP2C + Pyr1
3ujg – AtPP2C + SNRK2
3ujk – AtPP2C
ReferencesReferences
- ↑ Geiger D, Scherzer S, Mumm P, Stange A, Marten I, Bauer H, Ache P, Matschi S, Liese A, Al-Rasheid KA, Romeis T, Hedrich R. Activity of guard cell anion channel SLAC1 is controlled by drought-stress signaling kinase-phosphatase pair. Proc Natl Acad Sci U S A. 2009 Dec 15;106(50):21425-30. doi:, 10.1073/pnas.0912021106. Epub 2009 Dec 2. PMID:19955405 doi:10.1073/pnas.0912021106
- ↑ Sato A, Sato Y, Fukao Y, Fujiwara M, Umezawa T, Shinozaki K, Hibi T, Taniguchi M, Miyake H, Goto DB, Uozumi N. Threonine at position 306 of the KAT1 potassium channel is essential for channel activity and is a target site for ABA-activated SnRK2/OST1/SnRK2.6 protein kinase. Biochem J. 2009 Dec 10;424(3):439-48. doi: 10.1042/BJ20091221. PMID:19785574 doi:10.1042/BJ20091221
- ↑ Nakashima K, Fujita Y, Kanamori N, Katagiri T, Umezawa T, Kidokoro S, Maruyama K, Yoshida T, Ishiyama K, Kobayashi M, Shinozaki K, Yamaguchi-Shinozaki K. Three Arabidopsis SnRK2 protein kinases, SRK2D/SnRK2.2, SRK2E/SnRK2.6/OST1 and SRK2I/SnRK2.3, involved in ABA signaling are essential for the control of seed development and dormancy. Plant Cell Physiol. 2009 Jul;50(7):1345-63. doi: 10.1093/pcp/pcp083. Epub 2009, Jun 18. PMID:19541597 doi:10.1093/pcp/pcp083
- ↑ Furihata T, Maruyama K, Fujita Y, Umezawa T, Yoshida R, Shinozaki K, Yamaguchi-Shinozaki K. Abscisic acid-dependent multisite phosphorylation regulates the activity of a transcription activator AREB1. Proc Natl Acad Sci U S A. 2006 Feb 7;103(6):1988-93. Epub 2006 Jan 30. PMID:16446457 doi:10.1073/pnas.0505667103
- ↑ Fujii H, Verslues PE, Zhu JK. Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell. 2007 Feb;19(2):485-94. Epub 2007 Feb 16. PMID:17307925 doi:tpc.106.048538
- ↑ Hrabak EM, Chan CW, Gribskov M, Harper JF, Choi JH, Halford N, Kudla J, Luan S, Nimmo HG, Sussman MR, Thomas M, Walker-Simmons K, Zhu JK, Harmon AC. The Arabidopsis CDPK-SnRK superfamily of protein kinases. Plant Physiol. 2003 Jun;132(2):666-80. PMID:12805596 doi:10.1104/pp.102.011999
- ↑ Umezawa T, Sugiyama N, Mizoguchi M, Hayashi S, Myouga F, Yamaguchi-Shinozaki K, Ishihama Y, Hirayama T, Shinozaki K. Type 2C protein phosphatases directly regulate abscisic acid-activated protein kinases in Arabidopsis. Proc Natl Acad Sci U S A. 2009 Oct 13;106(41):17588-93. doi:, 10.1073/pnas.0907095106. Epub 2009 Sep 29. PMID:19805022 doi:10.1073/pnas.0907095106
- ↑ 12468729
- ↑ Belin C, de Franco PO, Bourbousse C, Chaignepain S, Schmitter JM, Vavasseur A, Giraudat J, Barbier-Brygoo H, Thomine S. Identification of features regulating OST1 kinase activity and OST1 function in guard cells. Plant Physiol. 2006 Aug;141(4):1316-27. Epub 2006 Jun 9. PMID:16766677 doi:pp.106.079327
- ↑ Belin C, de Franco PO, Bourbousse C, Chaignepain S, Schmitter JM, Vavasseur A, Giraudat J, Barbier-Brygoo H, Thomine S. Identification of features regulating OST1 kinase activity and OST1 function in guard cells. Plant Physiol. 2006 Aug;141(4):1316-27. Epub 2006 Jun 9. PMID:16766677 doi:pp.106.079327
- ↑ Belin C, de Franco PO, Bourbousse C, Chaignepain S, Schmitter JM, Vavasseur A, Giraudat J, Barbier-Brygoo H, Thomine S. Identification of features regulating OST1 kinase activity and OST1 function in guard cells. Plant Physiol. 2006 Aug;141(4):1316-27. Epub 2006 Jun 9. PMID:16766677 doi:pp.106.079327