Open AccessThe intracellular pathway and assembly of newly formed variable surface glycoprotein of Trypanosoma brucei.
Author(s) -
Dennis J. Grab,
Paul Webster,
Y Verjee
Publication year - 1984
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.81.24.7703
Subject(s) - trypanosoma brucei , golgi apparatus , endoplasmic reticulum , glycoprotein , biology , biochemistry , membrane , biophysics , microbiology and biotechnology , gene
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].