Multiple roles of pleckstrin homology domains in phospholipase Cbeta function

Since their discovery almost 10 years ago pleckstrin homology (PH) domains have been identified in a wide variety of proteins. Here, we focus on two proteins whose PH domains play a defined functional role, phospholipase C (PLC)-beta(2) and PLCdelta(1). While the PH domains of both proteins are responsible for membrane targeting, their specificity of membrane binding drastically differs. However, in both these proteins the PH domains work to modulate the activity of their catalytic core upon interaction with either phosphoinositol lipids or G protein activators. These observations show that these PH domains are not simply binding sites tethered onto their host enzyme but are intimately associated with their catalytic core. This property may be true for other PH domains.