Signaling with Phosphoinositides: Better than Binary

Structure of the PI3,4,5P₃-bound PH domain of Grp1. The conserved seven stranded β-barrel fold of the PH domain is augmented by an additional hairpin shown at the lower left corner of the backbone ribbon. The inositol ring contains phospates at the 1-, 3-, 4-, and 5- positions and is bound by arginine and lysine side chains (blue) and a histidine (green), with the novel hairpin enclosing the 5-phosphate. (See (45).)