Major surface glycoproteins of procyclic stage African trypanosomes

The procyclic stage in the life cycle of African trypanosomes is adapted for life in the harsh environment of the midgut of the tsetse fly vector. Procyclic forms derived by transformation from antigenically distinct bloodstream variants are antigenically similar and have lost the variant surface glycoprotein coat of the bloodstream forms. In contrast to bloodstream forms, where the variant surface glycoprotein coat is essentially the only molecule exposed, many different proteins can be labeled by surface iodination or biotinylation of procyclic trypanosomes. Despite this multiplicity of procyclic surface proteins, only a few have been characterized in any detail. This minireview focuses on one set of them, the predominant procyclins.