SURFACE-RECEPTORS AND TRANSPORTERS OF TRYPANOSOMA-BRUCEI

African trypanosomes combine antigenic variation of their surface coat with the ability to take up nutrients from their mammalian hosts. Upt ake of small molecules such as glucose or nucleosides is mediated by t ranslocators hidden from host antibodies by the surface coat. The mult iple glucose transporters acid transporters for nucleobases and nucleo sides have been characterized. Receptors for host macromolecules such as transferrin and lipoproteins are visible to antibodies but hidden f rom the cellular arm of the host immune system in an invagination of t he trypanosome surface, the flagellar pocket. The trypanosomal transfe rrin receptor is a heterodimer that resembles the major component of t he surface coat of Trypanosoma brucei. The ability to make several ver sions of this receptor allows T. brucei to bind transferrins from a ra nge of mammals with high affinity. The proteins required for uptake of nutrients by trypanosomes provide a target for chemotherapy that rema ins to be fully exploited.