Analyse du mécanisme fonctionnel de la chaperone/insertase tamA impliquée dans le repliement des protéines membranaires
Bibliographic record
Abstract
Le module de translocation et d'assemblage (TAM) participe au repliement des protéines de la membrane externe (OMPs) chez les bactéries Gram négatives. Malgré plus d'une décennie de travaux depuis sa découverte, son mécanisme reste inconnu. La modélisation moléculaire a identifié deux arginines dans la porte latérale de la sous-unité TamA comme étant des sites d'interactions aux phospholipides conservés. Ces arginines empêcheraient les lipides d'entrer dans le tonneau et contribueraient à l'activité insertase de la protéine. Ici, un modèle de protéoliposome a été utilisé pour mesurer l'influence de TamA sur le repliement des OMPs. Les tests d'activité insertase ont montré que l'intégration de TamA dans le liposome ne catalyse pas l'assemblage et l'insertion d'OmpX dans la bicouche lipidique. Cela pourrait être dû au fait que l'OmpX ne fait pas partie des substrats de TamA ou que TamA a besoin de sa protéine partenaire TamB pour fonctionner. En outre, des cristaux de TamA avec des substrats lipidiques PG14 ou Lyso PG14 ont été produits pour valider l'interaction des arginines conservées avec des lipides. Aucun cristal obtenu par co-cristallisation n'a fourni de données suffisantes pour résoudre la structure, vraisemblablement parce que les lipides entravent la nucléation et la croissance des cristaux de TamA. The translocation and assembly module (TAM) participates in the folding of outer membrane proteins (OMPs) in Gram negative bacteria. Despite over a decade of work since its discovery, its mechanism remains unknown. Molecular modelling identified two arginines in lateral gate of the TamA subunit as conserved phospholipid interactions sites. These arginines would prevent lipids from entering the barrel and contribute to the insertase activity of the protein. Here, a proteoliposome model was used to measure how TamA influences OMP folding. Insertase activity tests revealed that integrating TamA into the liposome doesn’t catalyse the assembly and insertion of OmpX into the lipid bilayer. This could be due to OmpX not being one of TamA’s substrate or to TamA needing its partner protein TamB in order to function. Furthermore, TamA crystals with lipids substrates PG14 or Lyso PG14 were produced to assess the interaction of the conserved arginines with lipids. No crystals obtained from co-crystallisation method yielded sufficient diffraction data to resolve a crystal structure likely due to lipids impeding TamA crystal nucleation and growth.
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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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".