Determination of the disulfide bonds within a B domain variant surface glycoprotein from Trypanosoma congolense.

The disulfide bonds within a variant surface glycoprotein from Trypanosoma congolense have been determined. L-[35S]Cysteine metabolically labeled protein was digested with trypsin, and radiolabeled peptides were separated by reversed-phase high performance liquid chromatography, and putative cystine-containing peptides were subdigested with other proteases and analyzed after further purification by amino acid sequencing and mass spectrometry. All eight cysteine residues of the protein, located within the N-terminal domain, are covalently linked.

Glycosyl-phosphatidylinositols of Trypanosoma congolense: two common precursors but a new protein-anchor.

The parasitic protozoan Trypanosoma congolense exhibits a dense surface coat which is pivotal for immunoevasion of the parasite. This dense surface coat is made of a single protein species, the variant surface glycoprotein, which is present in a high copy number. The protein is anchored to the plasma membrane by a glycosyl-phosphatidylinositol membrane anchor.

Sequence determination of three variable surface glycoproteins from Trypanosoma congolense. Conserved sequence and structural motifs.

The full-length cDNA sequences of three variable surface glycoproteins from bloodstream forms of Trypanosoma congolense have been determined. They encode preproteins of 429, 449, and 428 amino acids. These proteins contain the typical N-terminal leader sequences of secreted eukaryotic proteins, and display hydrophobic amino acids at their C-termini characteristic of variable surface glycoproteins; these leader sequences serve as transient membrane anchors after protein synthesis.

Trypanosoma congolense bloodstream forms evade complement lysis in vitro by shedding of immune complexes.

In the presence of antibodies against the variant surface glycoprotein (VSG) and guinea pig complement, Trypanosoma congolense bloodstream forms were lysed. Parasites, which had been preincubated with antibodies at 37 degrees C before addition of complement, escaped from complement lysis in a time- and temperature-dependent process. Preincubation caused removal of the antibodies from the cell surface by formation of filopodia and accumulation of the immune complexes between aggregated cells.