The architecture of the multisubunit TRAPP I complex suggests a model for vesicle tethering.
Transport protein particle (TRAPP) I is a multisubunit vesicle tethering factor composed of seven subunits involved in ER-to-Golgi trafficking. The functional mechanism of the complex and how the subunits interact to form a functional unit are unknown. Here, we have used a multidisciplinary approach that includes X-ray crystallography, electron microscopy, biochemistry, and yeast genetics to elucidate the architecture of TRAPP I. The complex is organized through lateral juxtaposition of the subunits into a flat and elongated particle. We have also localized the site of guanine nucleotide exchange activity to a highly conserved surface encompassing several subunits. We propose that TRAPP I attaches to Golgi membranes with its large flat surface containing many highly conserved residues and forms a platform for protein-protein interactions. This study provides the most comprehensive view of a multisubunit vesicle tethering complex to date, based on which a model for the function of this complex, involving Rab1-GTP and long, coiled-coil tethers, is presented.
Kim
Yeon-Gil
YG
Center for Biomolecular Recognition and Division of Molecular and Life Sciences, Department of Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, South Korea.
Raunser
Stefan
S
Munger
Christine
C
Wagner
John
J
Song
Young-Lan
YL
Cygler
Miroslaw
M
Walz
Thomas
T
Oh
Byung-Ha
BH
Sacher
Michael
M
D000596:Amino Acids; D000818:Animals; D008565:Membrane Proteins / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism* / Q000648:ultrastructure
D000596:Amino Acids; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D021122:Protein Subunits; D011994:Recombinant Proteins; C496933:Trappc3 protein, mouse; D033921:Vesicular Transport Proteins; C406327:transport protein particle, TRAPP