The PX domain is a phosphoinositide-binding structural domain involved in targeting of proteins to cell membranes.

[1][2] It was also identified in many other proteins involved in membrane trafficking, including nexins, Phospholipase D, and phosphoinositide-3-kinases.

The PX domain is structurally conserved in eukaryotes, although amino acid sequences show little similarity.

[3] PX domains interact primarily with PtdIns(3)P lipids.

The PX-domain can also interact with other domains and proteins.