Outer Membrane Protein OmpW Participates with Small Multidrug Resistance Protein Member EmrE in Quaternary Cationic Compound Efflux
Bibliographic record
Abstract
In Escherichia coli, the small multidrug resistance (SMR) transporter protein EmrE confers host resistance to a broad range of toxic quaternary cation compounds (QCC) via proton motive force in the plasma membrane. Biologically produced QCC also act as EmrE osmoprotectant substrates within the cell and participate in host pH regulation and osmotic tolerance. Although E. coli EmrE is one of the most well-characterized SMR members, it is unclear how the substrates it transports into the periplasm escape across the outer membrane (OM) in Gram-negative bacteria. We tested the hypothesis that E. coli EmrE relies on an unidentified OM protein (OMP) to complete the extracellular release of its QCC. Eleven OMP candidates were screened using an alkaline phenotypic growth assay to identify OMP involvement in EmrE-mediated QCC efflux. E. coli single-gene deletion strains were transformed with plasmid-carried copies of emrE to detect reduced-growth and rescued-growth phenotypes under alkaline conditions. Among the 11 candidates, only the ΔompW strain showed rescued alkaline growth tolerance when transformed with pEmrE, supporting the corresponding protein's involvement in EmrE osmoprotectant efflux. Coexpression of plasmids carrying the ompW and emrE genes transformed into the E. coli ΔompW and ΔemrE strains demonstrated a functional complementation restoring the original alkaline loss-of-growth phenotype. Methyl viologen drug resistance assays of pEmrE and pOmpW plasmid-complemented E. coli ΔompW and wild-type strains found higher host drug resistance than with other plasmid combinations. This study confirms our hypothesis that the porin OmpW participates in the efflux of EmrE-specific substrates across the OM.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.000 | 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 teacher head, 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".