Report

Molecular Mimicry Regulates ABA Signaling by SnRK2 Kinases and PP2C Phosphatases

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Science  24 Nov 2011:
1215106
DOI: 10.1126/science.1215106

Abstract

Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and SnRK2 kinases. Here, we report a SnRK2–PP2C complex structure, which reveals a striking similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor–PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase–phosphatase regulation through mutual packing of their catalytic sites.