InterPro domain: IPR012990

COPII (coat protein complex II)-coated vesicles carry proteins from the endoplasmic reticulum (ER) to the Golgi complex [ 1 ]. COPII-coated vesicles form on the ER by the stepwise recruitment of three cytosolic components: Sar1-GTP to initiate coat formation, Sec23/24 heterodimer to select SNARE and cargo molecules, and Sec13/31 to induce coat polymerisation and membrane deformation [ 2 ].

Sec23 p and Sec24p are structurally related, folding into five distinct domains: a beta-barrel, a zinc-finger ( IPR006895 ), an alpha/beta trunk domain ( IPR006896 ), an all-helical region ( IPR006900 ), and a C-terminal gelsolin-like domain ( IPR007123 ). This entry describes part of the Sec23/24 beta-barrel domain, which is formed from approximately 180 residues from three segments of the polypeptide. The strands of the barrel are oriented roughly parallel to the membrane such that one end of the barrel forms part of the inner surface of the coat and the other end part of the membrane-distal surface. The barrel is constructed from two opposed sheets: a six-stranded beta sheet facing partly towards the zinc finger domain and partly towards the solvent, and a five-stranded beta sheet facing the helical domain.

1. Structure of the Sec23p/24p and Sec13p/31p complexes of COPII. Proc. Natl. Acad. Sci. U.S.A. 98, 10704-9
2. Structure of the Sec23/24-Sar1 pre-budding complex of the COPII vesicle coat. Nature 419, 271-7