Structural characterization of the Atg1 kinase complex by single particle electron microscopy
Bibliographic record
Abstract
In eukaryotes, autophagy is an evolutionarily conserved and essential “self-degradative” process used to maintain cellular homeostasis. Central to autophagy is the formation of double-membrane vesicles termed autophagosomes. The process of autophagosome formation is coordinated by over 35 autophagy-related (Atg) proteins. The Atg1 kinase complex constitutes one group of proteins required for the initial induction step of autophagosome formation. The Atg1 kinase complex is composed of the kinase Atg1, a regulatory phosphoprotein Atg13, and a protein scaffold Atg17 that forms a ternary complex with Atg31 and Atg29. In this study, we have determined the structure of the Saccharomyces cerevisiae Atg17-Atg31-Atg29 ternary complex by single-particle electron microscopy. The complex is an “S-shaped” dimer exhibiting an elongated architecture with an end-to-end distance of 345Å. Atg17 was found to form the central scaffold while Atg31 and Atg29 formed two globular densities tethered to the arcs formed by Atg17. Further analysis of purified Atg17 dimers showed that Atg17 mediated dimerization of the complex while Atg31 and Atg29 had a structural role in maintaining the distinct curvature of the complex. We further studied Atg1 kinase complex assembly by co-expressing a minimal pentameric assembly consisting of Atg1 CTD (residues 589-897) and Atg13 CTD (residues 384-738) with Atg17-Atg31-Atg29. Structural analysis localized Atg1 CTD and Atg13 CTD to the terminal regions of the ternary complex supporting that the N-terminus of Atg17 likely mediates complex assembly. Finally, we structurally characterized an important Atg1 kinase complex interacting partner, Atg11. Purified Atg11 exhibited an elongated architecture supporting its role as a coiled-coil protein scaffold.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".