Investigation of Escherichia coli Dimethyl Sulfoxide Reductase Assembly and Processing in Strains Defective for the sec-Independent Protein Translocation System Membrane Targeting and Translocation
Bibliographic record
Abstract
Dimethyl sulfoxide reductase is a heterotrimeric enzyme (DmsABC) localized to the cytoplasmic surface of the inner membrane. Targeting of the DmsA and DmsB catalytic subunits to the membrane requires the membrane targeting and translocation (Mtt) system. The DmsAB dimer is a member of a family of extrinsic, cytoplasmic facing membrane subunits that require Mtt in order to assemble on the membrane. We show that the MttA(2), MttB, and presumably MttA(1) but not the MttC proteins are required for targeting DmsAB to the membrane. Unlike other Mtt substrates such as trimethylamine N-oxide reductase, the soluble cytoplasmic DmsAB dimer that accumulates in the mtt deletions is very labile. Deletion of the mttA(2) or mttB genes also prevents anaerobic growth on fumarate even though fumarate reductase does not require Mtt for assembly. This was due to the lethality of membrane insertion of DmsC in the absence of the DmsAB subunits. In the absence of DmsC, DmsAB accumulates in the cytoplasm. A 45-amino acid leader on DmsA is removed during assembly. Processing does not require DmsC but does require Mtt. Translocation of DmsAB to the periplasm is not required for processing. The leader may be cleaved by a novel leader peptidase, or the long DmsA leader may traverse the membrane through the Mtt system resulting in cleavage by the periplasmic leader peptidase I followed by release of DmsA into the cytoplasm.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 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".