Assembly of the MexAB-OprM Multidrug Pump of <i>Pseudomonas aeruginosa</i> : Component Interactions Defined by the Study of Pump Mutant Suppressors
Bibliographic record
Abstract
In an effort to identify key domains of the Pseudomonas aeruginosa MexAB-OprM drug efflux system involved in component interactions, extragenic suppressors of various inactivating mutations in individual pump constituents were isolated and studied. The multidrug hypersusceptibility of P. aeruginosa expressing MexB with a mutation in a region of the protein implicated in oligomerization (G220S) was suppressed by mutations in the alpha/beta domain of MexA. MexB(G220S) showed a reduced ability to bind MexA in vivo while representative MexA suppressors (V66M and V259F) restored the MexA-MexB interaction. Interestingly, these suppressors also restored resistance in P. aeruginosa expressing OprM proteins with mutations at the proximal (periplasmic) tip of OprM that is predicted to interact with MexB, suggesting that these suppressors generally overcame defects in MexA-MexB and MexB-OprM interaction. The multidrug hypersusceptibility arising from a mutation in the helical hairpin of MexA implicated in OprM interaction (V129M) was suppressed by mutations (T198I and F439I) in the periplasmic alpha-helical barrel of OprM. Again, the MexA mutation compromised an in vivo interaction with OprM that was restored by the T198I and F439I substitutions in OprM, consistent with the hairpin domain mediating MexA binding to this region of OprM. Interestingly, these OprM suppressor mutations restored multidrug resistance in P. aeruginosa expressing MexB(G220S). Finally, the oprM(T198I) suppressor mutation enhanced the yields of all three constituents of a MexA-MexB-OprM(T198I) pump as detected in whole-cell extracts. These data highlight the importance of MexA and interactions with this adapter in promoting MexAB-OprM pump assembly and in stabilizing the pump complex.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".