The ATG7 dimer with bound LC3 binds ATG3. Deletion mutagenesis, biochemical data and modeling suggest that recruitment of ATG3 to the ATG7 N-terminal FAP domain results in presentation of the ATG3 active site to the LC3-ATG7 thioester linkage from the opposing monomer in the ATG7 dimer (Tanida et al. 2012, Klionsky & Schulman 2014). The activated LC3 protein is transferred to the E2-like enzyme ATG3 through a thioester bond (Ichimura et al. 2000).