Protein Phosphatase 2C

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|'''Left panel''' - ABI1 [[3ujk]]

|'''Middle panel'''- HAB1 bound to PYL2^'''.'''ABA [[3ujl]]<br>

|'''Right panel''' - HAB1 (gold), with Mg²⁺ and SO₄^2- in complex with SnRK2.6 (blue) [[3ujg]]

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| <applet load='3ujk' size='300' frame='true' align='left' caption='3kdh - apo-Pyl2' scene = '56/564059/Apopyl2/1'/><br clear='both'>'''3kdh scenes''' <Br>

|<applet load='3ujl' size='300' frame='true' align='left' caption='3ujl - PYR2-HAB1' scene = '56/564059/Pyl2hab1/2' /><Br clear='both'>'''3ujl scenes'''<Br><scene name='56/564059/Pyl2hab1/1'>1. Default scene</scene> Complex between PYL2 (blue) with bound ABA (CPK spheres)and HAB1 (gold), a protein phosphatase 2C. Magnesium ions in the active site of HAB1 are shown as green spheres. <br><scene name='56/564059/Pyl2hab1/5'>2. Closed gate locked by interaction with HAB1</scene> Gate residue proline 92 (blue ball and stick) interacts with typtophan 290 (gold ball and stick and residues in a hydrophobic loop (dark gold ball and stick) of HAB1. The gate also interacts with residues surrounding the phosphatase's active site, which is marked by magnesium ions (small green spheres).

| <applet load='3ujg' size='300' frame='true' align='left' caption='3ujg - SnRK2.6-HAB1' scene = '55/559985/Aposnrk2_6/2' /><Br clear='both'>'''3ujg scenes'''<Br><scene name='55/559985/Aposnrk2_6/2'>1. Default Scene</scene> The two enzymes are bound via interface their active sites. The phosphatase inactivates the kinase by dephosphorylating the kinase activation loop and by sterically blocking the kinase active site. The complex was constructed as a fusion protein with a 6His-tag at the N-terminus of SnRK2.6 (residues 11–362) fused to HAB1(172–511) via a GSGSAGSAAGS linker. Mutations of D296A and E297A in SnRK2.6 were introduced at the crystal packing interface to reduce surface entropy. <br><scene name='55/559985/Ost1hab1_critical/3'>2. Important structures in SnRK2.6</scene> The same structures as in the left scene are shown. The fully resolved activation segment extends into the phosphatase's active site and is unphosphorylated. Residues 319-362 of SnRK2.6, which includes the ABA box, and the GSGSAGSAAGS linker are not resolved. The disorganization of the residues shown in ball and stick, with most pointing away from the active site, indicates that the catalytic domain is in the inactive state.<Br><scene name='55/559985/Ost1hab1_interaction/2'>3. Zone of interaction</scene> The activation loop (blue trace) of SnRK2.6 is inserted into the catalytic site (marked by the magnesium ions) of the phosphatase. The phosphorylatable residue of the activation loop S175 (CPK ball and stick) is positioned near the magnesium ions. W385 of the phosphatase (brown ball and stick) in turn protrudes into the kinase's active site, where it interacts with residues R139 and Glu144 (CPK ball and stick) of the catalytic loop (orchid trace) and I183 of the activation loop.<br><scene name='55/559985/Tetherbinding/1'> 5. Proposed interaction zone </scene> SnRK2.6 is shown in blue cartoon, and HAB1 in gold spacefill. The ABA box sequence is not resolved, but it would extend from the C-terminal end of the SNRK2 box helix (cyan helix). It is proposed that the ABA box sequence, which is highly acidic, binds to a patch of basic residues (blue) on the surface of the phosphatase.<ref name= "Soon2012"/>

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