The amino-acid sequence of ATG12 ends with a glycine residue that does not require protease activation. ATG12 is activated by the formation of a thioester bond between the ATG12 C-terminal Gly-140 and Cys-572 of ATG7, which is functionally analogous to E1 enzymes in ubiquitination (Tanida et al. 1999, 2001). ATG7 has been shown to function in the form of a homodimer (Komatsu et al. 2001).