ATG5 is directly required for the import of aminopeptidase I via the cytoplasm-to-vacuole targeting pathway [1]. ATG5 is conjugated to ATG12; this conjugate exhibits E3 ligase-like activity which facilitates the lipidation of members of the LC3 family, and therefore autophagosome formation [2]. ATG5 comprises N- and C-terminal ubiquitin-like domains (UblA and UblB) that flank the helical-rich region (HBR). This is the UblB domain, found at the C-terminal [2,3].

1: Apg5p functions in the sequestration step in the cytoplasm-to-vacuole targeting and macroautophagy pathways. George MD, Baba M, Scott SV, Mizushima N, Garrison BS, Ohsumi Y, Klionsky DJ; Mol Biol Cell 2000;11:969-982. PMID:10712513

2: Structure of the human ATG12~ATG5 conjugate required for LC3 lipidation in autophagy. Otomo C, Metlagel Z, Takaesu G, Otomo T; Nat Struct Mol Biol. 2013;20:59-66. PMID:23202584

3: Structure of Atg5.Atg16, a complex essential for autophagy. Matsushita M, Suzuki NN, Obara K, Fujioka Y, Ohsumi Y, Inagaki F; J Biol Chem. 2007;282:6763-6772. PMID:17192262