ABSTRACT
Biomembranes are mixtures of lipids and proteins. An increasing number of proteins are known to be anchored to the membrane via the carboxy terminus, which is attached to the ethanolamine moiety of a glycosyl phosphatidylinositol (glycosyl-PI). Inositol glycophospholipids with the general structure lipid-phosphate-inositol-glycan have been isolated from plants, bacteria, yeast, protozoa, and mammalian cells. Some of these glycosyl-PIs serve in protozoa as well as in mammalian organisms to attach proteins to the cell surface, others give rise to a phospho-oligosaccharide, which might act as a mediator of some of the actions of insulin and the function of others remain to be determined. The fatty acids of the diacylglycerol group of the various glycosyl-PI anchors show a wide variation. As a rule, many glycosyl-PI anchors contain only or a majority of saturated fatty acids. An obvious function of glycosyl-PI anchors is to attach proteins to the membrane.
