GMx33: a novel family of trans-Golgi proteins identified by proteomics

Traffic. 2000 Dec;1(12):963-75.


The known functions of the Golgi complex include the sorting, packaging, post-translational modification, and transport of secretory proteins, membrane proteins, and lipids. Other functions still remain elusive to cell biologists. With the goal of identifying novel Golgi proteins, a proteomics project was undertaken to map the major proteins of the organelle using two-dimensional gels, to identify the unknowns using tandem mass spectrometry, and to screen for Golgi residents using GFP-fusion constructs. Multiple unknowns were identified, and the initial characterization of one of these proteins is reported here. GMx33 alpha is a member of a conserved family of cytosolic Golgi-associated proteins with no known homology to any known functional domain or protein. Biochemical analyses show that GMx33 alpha differentially partitions into all phases of multiple detergent extractions, and two-dimensional immunoblots reveal that there are multiple differentially modified forms of GMx33 alpha associated with the Golgi, several of which are phosphorylated. Evidence suggests that these post-translational modifications regulate its association with the Golgi. GMx33 alpha was not found on Golgi budded vesicles, and immuno-electron microscopy co-localizes GMx33 alpha to the trans-face on the same three cisternae as TGN38 in normal rat kidney cells. This work represents the preliminary characterization of a novel family of trans-Golgi-associated proteins.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Carrier Proteins / analysis
  • Carrier Proteins / chemistry*
  • Cell Line
  • Cell-Free System
  • Cloning, Molecular
  • Detergents
  • Electrophoresis, Gel, Two-Dimensional
  • Genes, Reporter
  • Glycoproteins*
  • Humans
  • Immunoblotting
  • Liver / chemistry
  • Membrane Glycoproteins / analysis
  • Membrane Proteins*
  • Molecular Sequence Data
  • Proteome / analysis*
  • Rats
  • Recombinant Fusion Proteins / analysis
  • Recombinant Fusion Proteins / chemistry
  • Sequence Alignment
  • trans-Golgi Network / chemistry*
  • trans-Golgi Network / metabolism


  • Carrier Proteins
  • Detergents
  • GMx33alpha protein, rat
  • Glycoproteins
  • Membrane Glycoproteins
  • Membrane Proteins
  • Proteome
  • Recombinant Fusion Proteins
  • TGOLN2 protein, human
  • Tgoln2 protein, rat