Ubiquitin-like modifier involved in autophagosomes formation. May mediate the delivery of the autophagosomes to the vacuole via the microtubule cytoskeleton. Interacts with ATG4 (By similarity). Interacts with ATI1 (PubMed:22580699). Constitutively expressed. Induced by sugar starvation. Gly-119 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.