The GlcNAc-PI de-N-acetylase of glycosylphosphatidylinositol (GPI) biosynthesis in <i>Trypanosoma brucei</i>

Glycosyl-phosphatidylinositol (GPI) membrane anchors are present in organisms at most stages of eukaryotic evolution, including protozoa, yeast, slime moulds, invertebrates and vertebrates, and are found on a diverse range of proteins. They are primarily responsible for the anchoring of cell-surface proteins in the plasma membrane (or in some cases to the topologically equivalent lumenal surface of secretory vesicles) and may be considered as an alternative to the hydrophobic transmembrane polypeptide anchor of type-1 integral membrane proteins (Fig. 1). Many other functions have been proposed (though some remain controversial) for GPI anchors, including roles in intracellular sorting, transmembrane signalling, and novel endocytic processes. Most of these proposed functions are dependent on the hypothesis that a GPI anchor might allow proteins to associate in specialised membrane microdomains. These putative functions, as well as the structure, biosynthesis and distribution of GPI anchors, have been extensively reviewed (Englund, 1993; McConville and Ferguson, 1993; Brown, 1993; Ferguson, 1994)