ATG8, also known as GABARAPL1, is a ubiquitin-like protein that has a crystal structure. ATG8 consists of a 5-stranded β-sheet, which is enclosed by two α-helices at one side and one α-helix at the other side and exhibits a conserved GABARAP domain. It functions in the formation of autophagosomal membranes. The transient conjugation of ATG8 to the autophagosomal membrane through a ubiquitin-like conjugation system is essential for autophagy in eukaryotes. Autophagy is induced upon nutrient depletion or rapamycin treatment and leads to the response of more than 30 autophagy-related (ATG) genes known so far, including ATG8.

ATG5 is an E2 ubiquitin ligase which is necessary for autophagy. Its expression is a relatively late event in the apoptotic process, occurring downstream of caspase activity, dramatically highly expressed in apoptotic cells. It is activated by ATG7, conjugates to ATG12 and associates with isolation membrane to form cup-shaped isolation membrane and autophagosome. The conjugate complex detaches from the membrane immediately before or after autophagosome formation is completed. ATG5 plays an important role in the apoptotic process, possibly within the modified cytoskeleton.