Glycosylphosphatidylinositol Anchors for Proteins and Phosphatidylinositol Mannosides

A novel phospholipase C was obtained from Bacillus cereus in 1976 with the specificity to act upon phosphatidylinositol (see separate webpage) to generate diacylglycerol and inositol phosphate. When this was tested with tissues a year or two later, it was found to release in addition a variety of proteins including 5’-nucleotidase and erythrocyte acetylcholinesterase. It was apparent that these and many other proteins were covalently attached to phosphatidylinositol located in the cellular membranes. By 1985, detailed evidence was obtained for various components linking phosphatidylinositol to cell surface proteins but especially in relation to acetylcholinesterase in various species and of surface glycoproteins in the parasitic protozoan Trypanosoma brucei, and by 1988 a complete structure of the last was obtained by M.A.J. Ferguson and colleagues. It soon became apparent that there was a basic general structure for what became known as the glycosylphosphatidylinositol(GPI)-anchored proteins. As the lipid component is much more complex than in other proteolipids, they are discussed separately here.