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. 2013 Oct 29;23(12):1369–1379. doi: 10.1038/cr.2013.143

Figure 4.

Figure 4

The structure of PP2CA revealed an uncharacterized CCCH zinc-finger motif. (A) The extra motif in PP2CA is a CCCH zinc-finger motif. Left panel: Structure comparison between PP2CA and ABI1 reveals a new motif in PP2CA. Three metal ions (orange) are observed at the active site of PP2CA, but only one (black) is seen in the PYL1-bound ABI1 (PDB code: 3KDJ). The extra structural motif in PP2CA is highlighted in orange. Right panel: the 2Fo-Fc electron density (blue mesh) of the metal and the surrounding four residues is contoured at 1.5 σ. The zinc ion is coordinated by three Cys and one His residues. (B) Point mutations of the zinc coordinating residues lead to significantly crippled phosphatase activities. The details for the phosphatase assay are described in Materials and Methods. (C) Sequence alignment of the nine members of Clade A PP2Cs in A. thaliana revealed the zinc-finger motif (shaded in purple) conserved in HAI1/2/3 in addition to PP2CA. Invariant and conserved residues are colored red and blue, respectively. The active site residues are shaded green. The secondary elements of the core structure of PP2Cs are shown above the sequences.