Ubiquitin-like modifier involved in cytoplasm to vacuole transport (Cvt) vesicles and autophagosomes formation. May mediate the delivery of the vesicles and autophagosomes to the vacuole via the microtubule cytoskeleton (By similarity). Ubiquitin-like modifier involved in autophagosomes formation. May mediate the delivery of the autophagosomes to the vacuole via the microtubule cytoskeleton. Interacts with ATG4. Constitutively expressed. The C-terminal 2 residues are removed by ATG4 to expose Gly-117 at the C-terminus. The C-terminal Gly is then amidated with phosphatidylethanolamine by an activating system similar to that for ubiquitin. Belongs to the ATG8 family.