Schematic representation of the major surface glycoconjugates of procyclic and metacyclic Trypanosoma. brucei. Variant surface glycoprotein (VSG) is the major component of the metacyclic form, and each molecule consists of two GPI-anchored N-glycosylated monomers (shaded ovals are the protein component). The surface of the procyclic form is densely covered with procyclins, which are GPI-anchored polypeptides with polyanionic repeat domains (shaded rectangle is the protein component). The anchor structures are detailed below the schematic.