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TRAPPII subunits are required for the specificity switch of a Ypt-Rab GEF.

Ypt-Rab GTPases are key regulators of the various steps of intracellular trafficking. Guanine nucleotide-exchange factors (GEFs) regulate the conversion of Ypt-Rabs to the GTP-bound state, in which they interact with effectors that mediate all the known aspects of vesicular transport. An interesting possibility is that Ypt-Rabs coordinate separate steps of the transport pathways. The conserved modular complex TRAPP is a GEF for the Golgi gatekeepers Ypt1 and Ypt31/32 (Refs 5-7). However, it is not known how Golgi entry and exit are coordinated. TRAPP comes in two configurations: the seven-subunit TRAPPI is required for endoplasmic reticulum-to-Golgi transport, whereas the ten-subunit TRAPPII functions in late Golgi. The two essential TRAPPII-specific subunits Trs120 and Trs130 have been identified as Ypt31/32 genetic interactors. Here, we show that they are required for switching the GEF specificity of TRAPP from Ypt1 to Ypt31. Moreover, a trs130ts mutation confers opposite effects on the intracellular localization of these GTPases. We suggest that the Trs120-Trs130 subcomplex joins TRAPP in the late Golgi to switch its GEF activity from Ypt1 to Ypt31/32. Such a 'switchable' GEF could ensure sequential activation of these Ypts, thereby coordinating Golgi entry and exit.

Pubmed ID: 17041589


  • Morozova N
  • Liang Y
  • Tokarev AA
  • Chen SH
  • Cox R
  • Andrejic J
  • Lipatova Z
  • Sciorra VA
  • Emr SD
  • Segev N


Nature cell biology

Publication Data

November 1, 2006

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM-45444

Mesh Terms

  • Biological Transport
  • Endoplasmic Reticulum
  • Golgi Apparatus
  • Guanine Nucleotide Exchange Factors
  • Guanosine Diphosphate
  • Membrane Proteins
  • Microscopy, Fluorescence
  • Models, Biological
  • Mutation
  • Protein Binding
  • Protein Subunits
  • Qc-SNARE Proteins
  • SNARE Proteins
  • Saccharomyces cerevisiae Proteins
  • Time Factors
  • Vesicular Transport Proteins
  • rab GTP-Binding Proteins