Cryo-EM analysis of the Staphylococcus aureus phenol-soluble modulin exporter PmtCD apo form in detergent micelles, nanodiscs and peptidiscs
Bibliographic record
Abstract
Staphylococci secrete amphipathic peptides known as phenol soluble modulins (PSMs) that play a variety of pathogenic roles including host cell membrane destruction, biofilm development, and the triggering of inflammatory responses. PSM export is facilitated by the essential ATP-binding cassette (ABC) transporter PmtCD, which also provides producer immunity toward the membrane-damaging PSMs. Here, we report cryo-EM structures of PmtCD in a nucleotide-free state using different membrane mimetics - detergent, nanodisc and peptidisc - all featuring the transmembrane domains in an open state with a remarkably expansive intervening lumen. The consistently sized lumen suggests the possibility for two α-helical amphipathic PSMs to pack and passage within. A continuous hydrophobic surface with no apparent single high affinity site is in keeping with the ability of PmtCD to export a variety of hydrophobic PSM peptide substrates. The ATP driven collapse of the PmtD lumen is consistent with the lateral access and extrusion mechanisms of related ABC transporters that translocate membrane embedded substrates. Along with a new ADP product complex and prior ATPγS-bound form, these structures provide insights into the export of PSMs and a foundation for design of trojan horse antimicrobials that target MRSA strains from within by blocking membranolytic PSM export.
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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) | 0.002 | 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".