InterPro domain: IPR006896

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, an all-helical region ( IPR006900 ), and a C-terminal gelsolin-like domain ( IPR007123 ). This entry describes the Sec23/24 alpha/beta trunk domain, which is formed from a single, approximately 250-residue segment plugged into the beta-barrel between strands beta-1 and beta-19. The trunk has an alpha/beta fold with a vWA topology, and it forms the dimer interface, primarily involving strand beta-14 on Sec23 and Sec24; in addition, the trunk domain of Sec23 contacts Sar1.

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