Glycosylation of the variant surface antigens of Trypanosoma brucei.

Abstract

The variant-specific protein that forms the surface coat of the bloodstage trypanosome of Trypanosoma brucei is a glycoprotein, with oligosaccharides attached by covalent linkage to specific residues in the protein. The organism is able to express sequentially individual genes from a large repertoire of surface antigen genes and glycosylation of each of these gene products has been shown by binding to lectins (Strickler et al. 1978), by the direct detection of specific sugars associated with the protein (Allsopp and Njogu 1974; Johnson and Cross 1977) or by the effects of various inhibitors of protein glycosylation on the biosynthesis of the protein (Strickler and Patton 1980; Rovis and Dube 1981). The variant-specific proteins of the related trypanosomes T. congolense (Rautenberg et al. 1981; Reinwald et al. 1981) and T. equiperdum (Baltz et al. 1977) are also glycosylated. The molecular basis of antigenic variation and the biochemistry of the variant surface glycoproteins (VSGs) have been reviewed recently (Turner 1982; Borst and Cross 1982; Englund et al. 1982). This chapter will describe what is known about the location, biosynthesis, processing and structure of the carbohydrate attached to VSGs of T. brucei and will assess their possible significance for the biology of the parasite.