Modular phosphoinositide-binding domains - their role in signalling and membrane trafficking

The membrane phospholipid phosphatidylinositol is the precursor of a family of lipid second-messengers, known as phosphoinositides, which differ in th e phosphorylation status of their inositol group. A major advance in unders tanding phosphoinositide signalling has been the identification of a number of highly conserved modular protein domains whose function appears to be t o bind various phosphoinositides. Such 'cut and pastel modules are found in a diverse array of multidomain proteins and recruit their host protein to specific regions in cells via interactions with phosphoinositides. Here, wi th particular reference to proteins involved in membrane traffic pathways, we discuss recent advances in our understanding of phosphoinasitide-binding domains.