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Structure and organization of coat proteins in the COPII cage.

Cell | Jun 29, 2007

http://www.ncbi.nlm.nih.gov/pubmed/17604721

COPII-coated vesicles export newly synthesized proteins from the endoplasmic reticulum. The COPII coat consists of the Sec23/24-Sar1 complex that selects cargo and the Sec13/31 assembly unit that can polymerize into an octahedral cage and deform the membrane into a bud. Crystallographic analysis of the assembly unit reveals a 28 nm long rod comprising a central alpha-solenoid dimer capped by two beta-propeller domains at each end. We construct a molecular model of the COPII cage by fitting Sec13/31 crystal structures into a recently determined electron microscopy density map. The vertex geometry involves four copies of the Sec31 beta-propeller that converge through their axial ends; there is no interdigitation of assembly units of the kind seen in clathrin cages. We also propose that the assembly unit has a central hinge-an arrangement of interlocked alpha-solenoids-about which it can bend to adapt to cages of variable curvature.

Pubmed ID: 17604721 RIS Download

Mesh terms: Animals | COP-Coated Vesicles | Cells, Cultured | Clathrin | Crystallography, X-Ray | Endoplasmic Reticulum | Golgi Apparatus | Macromolecular Substances | Membrane Proteins | Models, Molecular | Nuclear Pore Complex Proteins | Protein Structure, Secondary | Protein Structure, Tertiary | Protein Transport | Saccharomyces cerevisiae | Saccharomyces cerevisiae Proteins | Vesicular Transport Proteins