Ubiquitin-like modifier involved in autophagosomes formation. May mediate the delivery of the autophagosomes to the vacuole via the microtubule cytoskeleton. Interacts with ATG4B (PubMed:15178341). Interacts with NBR1 (PubMed:21606687). A number of isoforms are produced. According to EST sequences. Constitutively expressed. The C-terminal 3 residues are removed by ATG4 to expose Gly-117 at the C-terminus. This Gly-117 forms then a thioester bond with the 'Cys-558' of ATG7 (E1-like activating enzyme) before being transferred to the 'Cys-258' of ATG3 (the specific E2 conjugating enzyme), in order to be finally amidated with phosphatidylethanolamine. This lipid modification anchors ATG8 to autophagosomes. Belongs to the ATG8 family.