Working hypothesis for the function of Apg7p in the Apg12p conjugation system. Apg12p associates with Apg7p. The C-terminal Gly of Apg12p conjugates with Cys507 in Apg7p via a thioester bond in an ATP-dependent manner. The reaction occurs in the cytoplasm or on the cytoplasmic side of an Apg12p-associated compartment(s). Although the E2 enzyme has not been identified, one candidate is Apg10p.