GABARAP: Proteins and Enzymes

gamma-Aminobutyric Acid Receptor-associated Protein (GABARAP), also known as Apg8p1, is 117 amino acid (aa) protein with a predicted molecular weight of 14 kDa. It is a member of the GABARAP subfamily of the Autophagy-related 8 (Atg8) family of proteins. The GABARAP subfamily also includes GABARAPL1. GABARAP/Apg8p1 has 100% aa sequence identity with its mouse and rat orthologs and is orthologous to yeast Atg8. Atg8 family members show structural similarity with Ubiquitin, but lack aa sequence similarity. GABARAP/Apg8p1 was first described for its putative involvement GABA A Receptor trafficking. However, it is best known for its role in autophagy. GABARAP/Apg8p1 covalently attaches to phosphatidylethanolamine (PE) in the phagophore (autophagosome precursor) membrane using a Ubiquitin-like conjugation system that includes Ubiquitin-activating (E1)-, Ubiquitin-conjugating (E2)-, and Ubiquitin Ligase (E3)-like enzymes. Here it is involved in the later stages of autophagosome maturation. It may also be involved in cargo recruitment to autophagosomes.