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Cell. 2007 Jun 29;129(7):1325-36.

Structure and organization of coat proteins in the COPII cage.

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  • 1Howard Hughes Medical Institute and the Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

Abstract

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.

Comment in

  • Making COPII coats. [Cell. 2007]
PMID:
17604721
[PubMed - indexed for MEDLINE]
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