Figure 1.

(A) Electron density maps calculated from experimental phases after solvent flattening, contoured at 0.6σ. Blue electron density covers the protein, the density for the phosphoinositide ligand is shown in green, for clarity. The refined, final model is shown as stick representation. (B) Ribbon representation of the PDK1 PH domain (residues 409–549). The standard PH domain fold is coloured green and red (β strands and the C-terminal α helix, respectively). The extension on the N-terminus is coloured blue. The Ins(1,3,4,5)P₄ ligand is shown as a stick representation. A coloured, semitransparent surface covers the protein molecule. (C) Topology diagram of the PH domain of PDK1, coloured according to B. (D) Hydrophobic interactions of the six-stranded β sheet with the N-terminal α1′ helix. Hydrophobic residues on the six-stranded β sheet and on the α1′ helix are shown as a stick representation, as is the Ins(1,3,4,5)P₄ ligand.