A novel heterodimeric transferrin receptor encoded by a pair of VSG expression site-associated genes in T. brucei

Cell. 1994 Jul 15;78(1):75-86. doi: 10.1016/0092-8674(94)90574-6.

Abstract

In T. brucei, a transferrin-binding protein has been found to share sequence homology with pESAG-7 and -6, the products of two related genes present in the VSG gene polycistronic transcription unit. When expressed in Xenopus oocytes, they appear as N-glycosylated proteins secreted in the medium (pESAG-7) and GPI anchored to the membrane (pESAG-6). These proteins are able to homo- or heterodimerize, probably through association in the same orientation. Only heterodimers can bind Tf, possibly two molecules per dimer. A comparison of Tf binding to pESAG-7/6-expressing oocytes and trypanosomes suggests that pESAG-7/6 is the Tf receptor of the parasite. In trypanosomes, the majority of pESAG-7/6 is released from the membrane and associates, together with Tf, with a glycosylated matrix present in the lumen of the flagellar pocket. Both pESAG-7/6 and Tf are internalized via coated pits and vesicles. These observations suggest a novel mode of Tf binding and uptake in trypanosomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies, Protozoan
  • Cytoplasm / chemistry
  • Endocytosis
  • Genes, Protozoan
  • Glycoproteins*
  • Kinetics
  • Membrane Proteins / chemistry
  • Molecular Sequence Data
  • Oocytes
  • Peptides / chemical synthesis
  • Peptides / immunology
  • Protein Binding
  • Protein Conformation
  • Protozoan Proteins / analysis
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics
  • Protozoan Proteins / immunology
  • Protozoan Proteins / metabolism*
  • Receptors, Transferrin / chemistry
  • Receptors, Transferrin / genetics
  • Receptors, Transferrin / metabolism*
  • Recombinant Fusion Proteins / immunology
  • Trypanosoma brucei brucei / chemistry
  • Trypanosoma brucei brucei / genetics
  • Trypanosoma brucei brucei / metabolism*
  • Trypanosoma brucei brucei / ultrastructure
  • Variant Surface Glycoproteins, Trypanosoma / analysis
  • Variant Surface Glycoproteins, Trypanosoma / genetics
  • Variant Surface Glycoproteins, Trypanosoma / immunology
  • Variant Surface Glycoproteins, Trypanosoma / metabolism*
  • Xenopus laevis

Substances

  • Antibodies, Protozoan
  • Glycoproteins
  • Membrane Proteins
  • Peptides
  • Protozoan Proteins
  • Receptors, Transferrin
  • Recombinant Fusion Proteins
  • Variant Surface Glycoproteins, Trypanosoma
  • ESAG 7 protein, Trypanosoma brucei