Comparative Analysis of Protein Glycosylation Pathways in Humans and the Fungal Pathogen Candida albicans

Figure 3

The GPI anchorage pathway. GPIs are glycolopids that act as a membrane anchor for many cell surface proteins and are composed of an inositol molecule that is sequentially modified in the ER with a Man3GlcN glycan and phosphoethanolamine groups. Numbers show sequential steps for the synthesis of a Man3GlcN glycan bearing GPI. A GPI-transamidase complex acts upon the phosphoethanolamine group linked to the terminal mannose to add the surface protein. The C. albicans Smp3 adds a fourth mannose residue that is essential for protein transfer; but in humans it is not essential for transamidation and its expression appears to be restricted to brain and colon.