Related Experiment Video
Updated: May 27, 2026
07:20
Imaging ATG9A, a Multi-Spanning Membrane Protein
Published on: June 16, 2023
Structural basis of Atg8 activation by a homodimeric E1, Atg7
Nobuo N Noda1, Kenji Satoo, Yuko Fujioka
1Institute of Microbial Chemistry, Tokyo, Tokyo 141-0021, Japan. nn@bikaken.or.jp
Molecular Cell
|November 8, 2011
Summary
Autophagy enzyme Atg7, a noncanonical E1 enzyme, activates ubiquitin-like proteins. Structural studies reveal how Atg7 binds Atg8 and transfers it to E2 enzyme Atg3 for essential cellular processes.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- E1 enzymes are crucial for ubiquitin-like protein activation and conjugation.
- Atg7 is a unique E1 enzyme essential for autophagy, activating Atg8 and Atg12.
- Understanding Atg7's mechanism is key to elucidating autophagy pathways.
Purpose of the Study:
- To determine the structural basis of Atg7's function in activating and conjugating Atg8.
- To elucidate the mechanism of Atg8 transfer from Atg7 to the E2 enzyme Atg3.
Main Methods:
- X-ray crystallography to obtain high-resolution structures of Atg7 and its complexes.
- Solution structure determination of Atg8 bound to Atg7's extreme C-terminal domain (ECTD).
- Biochemical assays to confirm functional interactions and catalytic mechanisms.
Main Results:
- Crystal structures revealed full-length Atg7 and its C-terminal domain bound to Atg8 and MgATP.
- Solution structure showed Atg8 bound to Atg7's ECTD.
- Atg7's N-terminal domain (NTD) binds E2 enzyme Atg3, while the C-terminal domain mediates Atg8 activation and transfer via a thioester intermediate.
- Atg8 transfer occurs through a trans mechanism between protomers of the Atg7 dimer.
Conclusions:
- Atg7 utilizes distinct domains (NTD and C-terminal domain) for binding E2 and ubiquitin-like proteins.
- The study provides atomic-level insights into the noncanonical E1 enzyme Atg7's mechanism in autophagy.
- The findings clarify the intricate steps of Atg8 conjugation, essential for autophagosome formation.
Related Concept Videos
01:33Coat Assembly and GTPases
Vesicles incorporate different coat protein subunits in different cell locations, which changes the properties of the coat, such as the shape and geometry of the transport vesicles. Thus, vesicle coat proteins also play a significant role in cargo selection.
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...
01:22Activation and Inactivation of G Proteins
Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
01:14Rab Proteins
Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
01:45Tail-anchoring of Proteins in the ER Membrane
Tail-anchored, or TA, proteins are estimated to make up to 3-5% of membrane proteins found in the eukaryotic cell. Such proteins have a single transmembrane domain located approximately 30 amino acid residues upstream from the C-terminal end. As a result, the signal recognition particle (SRP) cannot guide a TA protein to the ER membrane for cotranslational insertion. Hence, they are integrated into the ER membrane post-translationally using their C-terminal end as the anchor. TA proteins...
01:19Allosteric Proteins-ATCase
Binding sites linkages can regulate a protein's function. For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
01:48ATP Synthase: Mechanism
In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...