Cell surface proteins carry out a number of important functions
including cell-cell recognition, cell adhesion, ion transport
and signal transduction. While many of these proteins
are attached via one or multiple hydrophobic transmembrane
domains, it has become recognised more recently that a significant
number of cell surface proteins are anchored to the
membrane by a lipid anchor [1]. The most common lipid
anchor is glycosyl-phosphatidylinositol (GPI) which consists
of a glycan linkage containing ethanolamine linked to the Cterminal
of the protein, three mannose residues and glucosamine
linked to the inositol group of phosphatidylinositol
which is embedded in the plasma membrane (Fig. 1). The
hydrophobic component of this structure has been shown to
be susceptible to cleavage from the protein by phosphatidylinositol-specific
phospholipase C (Ptdlns-PLC) [3]. A diverse
array of membrane proteins has been identified as GPI-anchored
including hydrolytic enzymes, mammalian and protozoal
antigens and cell adhesion molecules [4]. It is not clear as
to what function or property a GPI-anchor may confer upon
membrane proteins although several possibilities include prolonging
the cell surface half life, increased mobility in the