title: The crystal structure of Atg3, an autophagy-related ubiquitin carrier protein (E2) enzyme that mediates Atg8 lipidation.
abstract: Atg3 is an E2-like enzyme that catalyzes the conjugation of Atg8 and phosphatidylethanolamine (PE). The Atg8-PE conjugate is essential for autophagy, which is the bulk degradation process of cytoplasmic components by the vacuolar/lysosomal system. We report here the crystal structure of Saccharomyces cerevisiae Atg3 at 2.5-A resolution. Atg3 has an alpha/beta-fold, and its core region is topologically similar to canonical E2 enzymes. Atg3 has two regions inserted in the core region, one of which consists of approximately 80 residues and has a random coil structure in solution and another with a long alpha-helical structure that protrudes from the core region as far as 30 A. In vivo and in vitro analyses suggested that the former region is responsible for binding Atg7, an E1-like enzyme, and that the latter is responsible for binding Atg8. A sulfate ion was bound near the catalytic cysteine of Atg3, suggesting a possible binding site for the phosphate moiety of PE. The structure of Atg3 provides a molecular basis for understanding the unique lipidation reaction that Atg3 carries out.
authors.affiliation: Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, N-12, W-6, Kita-ku, Sapporo 060-0812, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Yamada
authors.forename: Nobuo N
authors.initials: NN
authors.lastname: Suzuki
authors.forename: Takao
authors.initials: T
authors.lastname: Hanada
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Ichimura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kumeta
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fujioka
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: Fuyuhiko
authors.initials: F
authors.lastname: Inagaki
mesh_terms: D000595:Amino Acid Sequence; D001343:Autophagy; D000071193:Autophagy-Related Protein 7; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D005982:Glutathione Transferase / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry*
chemical_list: C114830:ATG7 protein, S cerevisiae; C113757:ATG8 protein, S cerevisiae; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; D044763:Ubiquitin-Conjugating Enzymes; D005982:Glutathione Transferase; D000071193:Autophagy-Related Protein 7; C104235:ATG3 protein, S cerevisiae