PH domains and their ligands. Schematic representation of a typical PH domain is shown in panel A (Akt PH domain, residues 111-115 omitted, PDB code 1UNQ). The core β sandwich is colored in blue, C-terminal α helix in green, loops in light pink and the β1/β2 loop in orange. In panel B the PH domains from Grp1 (PDB code: 1FGY) and Akt (PDB code: 1UNQ) are aligned to highlight a unique structural feature (colored in red) of the Grp1 PH domain (shown in grey). The variable β1/β2 loops of CPH (PDB code: 1ZM0) and Akt (PDB code: 1UNQ) are illustrated in panel C and colored yellow and blue respectively. Black arrows highlight key differences in binding pockets. Panel D illustrates the differences between phosphoinositides and inositol phosphates. Phosphate groups are shown as red dots.