The intracellular pathway and assembly of newly formed variable surface glycoprotein of Trypanosoma brucei.
Pulse-chase experiments using L-[35S]methionine suggest that Trypanosoma brucei MITat 1.2 variable surface glycoprotein (VSG) synthesized in the rough endoplasmic reticulum, a process that takes 6-8 min, is shuttled to the Golgi complex 8 min later. Labeling of ultrathin frozen sections with affinity-purified anti-cross-reacting determinant (CRD) IgG followed by protein A-colloidal gold shows that the CRD is localized in the trans-Golgi region. cis-Golgi is not labeled. VSG, when solubilized by treatment with the detergent Nonidet P-40, behaves on sucrose density gradients as a non-membrane protein with a sedimentation value of 5 S. In contrast, VSG solubilized in the presence of Zwittergent TM 3-14 yielded several VSG-containing fractions greater than 5 S, and only the 5S fraction contained the CRD. Lack of the CRD in VSG complexes with sedimentation values greater than 5 S suggests that this determinant is either masked from antibody, perhaps by involvement in polymer formation, or represents the membrane form of VSG recently described by Cardoso de Almeida and Turner [Cardoso de Almeida, M. L. & Turner, M. J. (1983) Nature (London) 302, 349-352].
D000818:Animals; D001345:Autoradiography; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D005407:Flagella / Q000378:metabolism / Q000648:ultrastructure; D006023:Glycoproteins / Q000096:biosynthesis*; D007700:Kinetics; D008565:Membrane Proteins / Q000096:biosynthesis*; D008715:Methionine / Q000378:metabolism; D008854:Microscopy, Electron; D013462:Sulfur Radioisotopes; D014346:Trypanosoma brucei brucei / Q000378:metabolism*; D014643:Variant Surface Glycoproteins, Trypanosoma
D006023:Glycoproteins; D008565:Membrane Proteins; D013462:Sulfur Radioisotopes; D014643:Variant Surface Glycoproteins, Trypanosoma; D008715:Methionine