title: Structure of Atg5.Atg16, a complex essential for autophagy.
abstract: Atg5 is covalently modified with a ubiquitin-like modifier, Atg12, and the Atg12-Atg5 conjugate further forms a complex with the multimeric protein Atg16. The Atg12-Atg5.Atg16 multimeric complex plays an essential role in autophagy, the bulk degradation system conserved in all eukaryotes. We have reported here the crystal structure of Atg5 complexed with the N-terminal region of Atg16 at 1.97A resolution. Atg5 comprises two ubiquitin-like domains that flank a helix-rich domain. The N-terminal region of Atg16 has a helical structure and is bound to the groove formed by these three domains. In vitro analysis showed that Arg-35 and Phe-46 of Atg16 are crucial for the interaction. Atg16, with a mutation at these residues, failed to localize to the pre-autophagosomal structure and could not restore autophagy in Atg16-deficient yeast strains. Furthermore, these Atg16 mutants could not restore a severe reduction in the formation of the Atg8-phosphatidylethanolamine conjugate, another essential factor for autophagy, in Atg16-deficient strains under starvation conditions. These results taken together suggest that the direct interaction between Atg5 and Atg16 is crucial to the performance of their roles in autophagy.
authors.affiliation: Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, N-21, W-11, Kita-ku, Sapporo 001-0021, Japan.
authors.forename: Minako
authors.initials: M
authors.lastname: Matsushita
authors.forename: Nobuo N
authors.initials: NN
authors.lastname: Suzuki
authors.forename: Keisuke
authors.initials: K
authors.lastname: Obara
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: D000818:Animals; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000737:chemistry*; D046912:Multiprotein Complexes / Q000737:chemistry; D010714:Phosphatidylethanolamines; D011485:Protein Binding; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D025801:Ubiquitin; D015003:Yeasts
chemical_list: C498649:ATG16 protein, S cerevisiae; C502778:ATG5 protein, human; C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D010714:Phosphatidylethanolamines; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; C483858:phosphatidylethanolamine