The Coat Protein Complex II (COPII) mediates protein transport from the ER to Golgi (anterograde transport). COPII recruitment is initiated by the activation of the small GTPase
Sar1.
Sar1 recruits a heterodimeric complex comprising of Sec23/24, which interacts with cargo and the outer cage - a heterotetramer composed of Sec13/31. (Adapted from
PMID:18060556).