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The Structures of COPII Coats and Cages
Author(s) -
Stagg Scott Malone,
LaPointe Paul,
Razvi Abbas,
Gurkan Cemal,
Potter Clinton S,
Carragher Bridget,
Balch William E
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.877.5
Subject(s) - copii , copi , endoplasmic reticulum , biology , microbiology and biotechnology , tethering , signal transducing adaptor protein , vesicular transport proteins , vesicle , golgi apparatus , secretory pathway , membrane , signal transduction , biochemistry , intracellular , vacuolar protein sorting , endosome
Coat protein complex II (COPII) vesicles are responsible for packaging and transporting over 10,000 different cargo molecules (about one‐third of the eukaryotic genome) of widely varying sizes and shapes from the endoplasmic reticulum (ER) to downstream compartments of the secretory pathway. Proteins involved in generating COPII vesicles include the GTPase Sar1, the cargo adaptor Sec23/24, and the cage scaffold Sec13/31. We previously showed that Sec13/31 can self‐assemble into a novel cuboctahedron cage, leading us to suggest that Sec13/31 may form cages of increasing size based on the simple rule that the geometry of the cage is dictated by four Sec13/31 heterotetramers combining to form a vertex. We have now solved the structure of an icosidodecahedral COPII coat assembled from both Sec13/31 and Sec23/24 by cryo‐electron microscopy (cryoEM) and single particle reconstruction. This new structure reveals for the first time the structure of the adaptor layer and reveals possible mechanisms for the coordination of adaptor interaction with cage formation and for the collection of cargo of varying size. We fit a crystal structure of the Sec13/31 heterotetramer into the cuboctahedron and icosidodecahedron structures, and this lead us to propose a molecular mechanism by which the COPII system can accommodate cargo of diverse sizes and shapes.