Phosphoinositides

Unique properties among signaling molecules

• 7 distinct signals

Differential phosphorylation at the 3, 4, and 5 position on the inositol ring allows for the generation of seven distinct phosphoinositides. All seven are found naturally occurring in the cell membranes of all higher eukaryotes.

• Rapidly interconverted

Phosphoinositide kinases and phosphatases can rapidly convert one specific phosphoinositide into another.

• Source of other classes of signaling molecules

Inositol trisphosphate (IP3), diacylglycerol, and phosphatidic acid are among the signaling molecules that can be produced from phosphoinositides

• Membrane-bound/Well-suited to spatially restricted signaling

The lipid tail renders the phosphoinositides obligately membrane-bound. This makes them well-suited to mark particular membrane compartments, or subdomains within a membrane.