title: Structure of the Atg12-Atg5 conjugate reveals a platform for stimulating Atg8-PE conjugation.
abstract: Atg12 is conjugated to Atg5 through enzymatic reactions similar to ubiquitination. The Atg12-Atg5 conjugate functions as an E3-like enzyme to promote lipidation of Atg8, whereas lipidated Atg8 has essential roles in both autophagosome formation and selective cargo recognition during autophagy. However, the molecular role of Atg12 modification in these processes has remained elusive. Here, we report the crystal structure of the Atg12-Atg5 conjugate. In addition to the isopeptide linkage, Atg12 forms hydrophobic and hydrophilic interactions with Atg5, thereby fixing its position on Atg5. Structural comparison with unmodified Atg5 and mutational analyses showed that Atg12 modification neither induces a conformational change in Atg5 nor creates a functionally important architecture. Rather, Atg12 functions as a binding module for Atg3, the E2 enzyme for Atg8, thus endowing Atg5 with the ability to interact with Atg3 to facilitate Atg8 lipidation.
authors.affiliation: Microbial Chemistry Research Foundation, Laboratory of Molecular Structure, Institute of Microbial Chemistry, 3-14-23, Kamiosaki, Shinagawa-ku, Tokyo 141-0021, Japan. nn@bikaken.or.jp
authors.forename: Nobuo N
authors.initials: NN
authors.lastname: Noda
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fujioka
authors.forename: Takao
authors.initials: T
authors.lastname: Hanada
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: Fuyuhiko
authors.initials: F
authors.lastname: Inagaki
mesh_terms: D001343:Autophagy; D000071192:Autophagy-Related Protein 12; D000071187:Autophagy-Related Protein 5; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D054878:Lipoylation; D008869:Microtubule-Associated Proteins / Q000737:chemistry*; D008958:Models, Molecular; D010714:Phosphatidylethanolamines / Q000737:chemistry; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D011499:Protein Processing, Post-Translational; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry*
chemical_list: C491969:ATG12 protein, S cerevisiae; C498649:ATG16 protein, S cerevisiae; C102268:ATG5 protein, S cerevisiae; C113757:ATG8 protein, S cerevisiae; D000071192:Autophagy-Related Protein 12; D000071187:Autophagy-Related Protein 5; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins; D008869:Microtubule-Associated Proteins; D010714:Phosphatidylethanolamines; D029701:Saccharomyces cerevisiae Proteins; C483858:phosphatidylethanolamine; D044767:Ubiquitin-Protein Ligases