Figure 1
From: The PITP family of phosphatidylinositol transfer proteins
PITPs bind to PI and PC and transfer them between membrane compartments (for example, the endoplasmic reticulum and plasma membrane, as shown). PITPs were first purified by virtue of their ability to transfer PI between two membrane compartments in vitro. PITPs are always occupied by a single molecule of either phosphatidylinositol (PI) or phosphatidylcholine (PC). The affinity for PI is 16-fold higher than for PC, and depending on the relative distribution of PI and PC, PITPs can re-distribute PI at the expense of PC.