Figure 2. Overall structure of the nPP2Ac–α4 complex.

(a) Overall structure of the nPP2Ac–α4 complex and the symmetry-related heterodimer in ribbon. The nPP2Ac, α4 and their symmetry-related counterparts are coloured blue, magenta, green, and orange, respectively. (b) Structural overlay of the nPP2Ac–α4 complex and the active PP2A catalytic subunit (PDB accession code: 2IE3) by the N-terminal helix motif. The colour scheme is the same as in a, except that active PP2Ac is coloured cyan and the helix and loop switches are coloured yellow. Helices and β-strands are shown in tube and ribbon, respectively. α4 is shown in semi-transparent surface. Only helix 5 and 6 of α4 are shown in tube. Red spheres represent catalytic metal ions in active PP2Ac.