title: Secondary structure of the variant surface glycoproteins of trypanosomes.
abstract: The secondary structure of seven variant surface glycoproteins (VSGs) of trypanosomes has been determined by Raman spectroscopy. They are all predominantly alpha-helical, the alpha-helix content varying between 50 and 60%. The beta-strand content varies between 20 and 25%, and the content of beta-turn and nonregular structures is about 25%. For three VSGs the N-terminal domain obtained by proteolytic cleavage was found to have essentially the same secondary structure as the complete VSGs. For three VSGs a secondary structure prediction has been performed applying the rules of Chou and Fasman. In all cases, two long alpha-helices extending over about 50 residues or 80 A are predicted in agreement with the X-ray diffraction data of Freymann et al. [(1984) Nature 311, 167-169] and Metcalf et al. [(1987) Nature 325, 84-86]. The region between the two alpha-helical segments exhibits a high potential of beta-turns, suggesting that this segment may be exposed on the cell surface and carry major antigenic determinants.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006023:Glycoproteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman; D014345:Trypanosoma / Q000032:analysis*; D014346:Trypanosoma brucei brucei / Q000032:analysis; D014643:Variant Surface Glycoproteins, Trypanosoma
chemical_list: D006023:Glycoproteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D014643:Variant Surface Glycoproteins, Trypanosoma