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==Arabidopsis SnRK2.6 ( | ==SnRK2.6/OST1/SRK2E== | ||
SnRK2.6/OST1/SRK2E and its homologs are protein kinases that are activated by the abscisic acid (ABA) response pathway in plants. In unstimulated cells inactive SnRK2.6 is in a complex with a protein phosphatase 2C (ABI1 or its homologs). Upon its arrival in the cell, ABA binds to the ABA-receptor (PYR1/RCAR), and it in turn binds to the protein phosphatase, which releases active SnRK2.6 to phosphorylate its substrate proteins. Activation of this pathway by ABA leads to 1) phosphorylation of ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1 REF? in guard cells and stomatal closure; 2) phosphorylation of transcription factor ABI5 REF? in seeds/seedlings and dormancy/growth arrest; 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref>PMID: 17307925</ref> in vegetative tissue and stress tolerance and growth regulation. | |||
Names and family members | |||
Two of the protein kinase's three names originated from its membership in subclass III of the SnRK2 family of protein kinases. The Arabidopsis kinase was named SnRK2.6 by Hrabak et al and SRK2E by Umezawa et al<ref>PMID: 19805022</ref>. SnRK2 stands for SNF1-related kinase group 2, which in Arabidopsis has XX members. The third name OST1 (open stomata 1)<ref>12468729</ref> designated the phenotype of plants bearing a gene mutation that produced an inactive protein kinase. In rice the homologs of these kinases are named SAPK8, SAPK9 and SAPK10. | |||
Two other family members, 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 the members of the protein phosphatase 2C family, ABI1, HAB1 or HAB2. | |||
Clearest picture of Pyr1 gate - latch is in Annu Reviews article | |||
<Structure load='3UC4' size='400' frame='true' align='left' caption='3uc4 - apo SnRK2.6' scene='55/559985/Aposnrk2_6/3' /> | <Structure load='3UC4' size='400' frame='true' align='left' caption='3uc4 - apo SnRK2.6' scene='55/559985/Aposnrk2_6/3' /> | ||
Revision as of 20:18, 25 September 2013
SnRK2.6/OST1/SRK2ESnRK2.6/OST1/SRK2E
SnRK2.6/OST1/SRK2E and its homologs are protein kinases that are activated by the abscisic acid (ABA) response pathway in plants. In unstimulated cells inactive SnRK2.6 is in a complex with a protein phosphatase 2C (ABI1 or its homologs). Upon its arrival in the cell, ABA binds to the ABA-receptor (PYR1/RCAR), and it in turn binds to the protein phosphatase, which releases active SnRK2.6 to phosphorylate its substrate proteins. Activation of this pathway by ABA leads to 1) phosphorylation of ion channels SLAC1[1] and KAT1 REF? in guard cells and stomatal closure; 2) phosphorylation of transcription factor ABI5 REF? in seeds/seedlings and dormancy/growth arrest; 3) phosphorylation of transcription factor AREB/ABF [2][3] in vegetative tissue and stress tolerance and growth regulation.
Names and family members Two of the protein kinase's three names originated from its membership in subclass III of the SnRK2 family of protein kinases. The Arabidopsis kinase was named SnRK2.6 by Hrabak et al and SRK2E by Umezawa et al[4]. SnRK2 stands for SNF1-related kinase group 2, which in Arabidopsis has XX members. The third name OST1 (open stomata 1)[5] designated the phenotype of plants bearing a gene mutation that produced an inactive protein kinase. In rice the homologs of these kinases are named SAPK8, SAPK9 and SAPK10.
Two other family members, 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 the members of the protein phosphatase 2C family, ABI1, HAB1 or HAB2.
Clearest picture of Pyr1 gate - latch is in Annu Reviews article
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SNRK2 box is a C-terminal motif that is common to all SNRK2s. It forms a helix that parallels subdomain III.
Activation loop (with gap) in blue
Catalytic loop in orchid
C-helix in yellow
K in chartreuse
Snrk2 box (unique to Snrk's) in turquoise.
C-terminal acidic domain missing.
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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
ABA box is acidic sequence in C-terminus that is common to SNRK2s that are regulated by ABA. This sequence binds to PP2C in biochemical assays, but is not seen in the crystal structure.
kinase activation loop in blue
phosphatase W385 in brown
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