title: Atg8 transfer from Atg7 to Atg3: a distinctive E1-E2 architecture and mechanism in the autophagy pathway.
abstract: Atg7 is a noncanonical, homodimeric E1 enzyme that interacts with the noncanonical E2 enzyme, Atg3, to mediate conjugation of the ubiquitin-like protein (UBL) Atg8 during autophagy. Here we report that the unique N-terminal domain of Atg7 (Atg7(NTD)) recruits a unique "flexible region" from Atg3 (Atg3(FR)). The structure of an Atg7(NTD)-Atg3(FR) complex reveals hydrophobic residues from Atg3 engaging a conserved groove in Atg7, important for Atg8 conjugation. We also report the structure of the homodimeric Atg7 C-terminal domain, which is homologous to canonical E1s and bacterial antecedents. The structures, SAXS, and crosslinking data allow modeling of a full-length, dimeric (Atg7~Atg8-Atg3)(2) complex. The model and biochemical data provide a rationale for Atg7 dimerization: Atg8 is transferred in trans from the catalytic cysteine of one Atg7 protomer to Atg3 bound to the N-terminal domain of the opposite Atg7 protomer within the homodimer. The studies reveal a distinctive E1~UBL-E2 architecture for enzymes mediating autophagy.
authors: Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
authors: Asad M
authors: AM
authors: Taherbhoy
authors: Stephen W
authors: SW
authors: Tait
authors: Stephen E
authors: SE
authors: Kaiser
authors: Allison H
authors: AH
authors: Williams
authors: Alan
authors: A
authors: Deng
authors: Amanda
authors: A
authors: Nourse
authors: Michal
authors: M
authors: Hammel
authors: Igor
authors: I
authors: Kurinov
authors: Charles O
authors: CO
authors: Rock
authors: Douglas R
authors: DR
authors: Green
authors: Brenda A
authors: BA
authors: Schulman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001343:Autophagy; D000071193:Autophagy-Related Protein 7; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D018360:Crystallography, X-Ray; D005347:Fibroblasts / Q000201:enzymology* / Q000473:pathology; D057927:Hydrophobic and Hydrophilic Interactions; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D009154:Mutation; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C502661:Atg7 protein, mouse; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins; C407740:Gabarapl2 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D009097:Multienzyme Complexes; D011993:Recombinant Fusion Proteins; D044763:Ubiquitin-Conjugating Enzymes; D000071193:Autophagy-Related Protein 7; C568853:Atg3 protein, mouse