Exploring GTP Control of Bacterial Respiratory System Specific Chaperone Interaction with its Substrate Protein's Twin‐Arginine Signal Peptide
Bibliographic record
Abstract
Many bacterial respiratory redox enzymes depend on the twin‐arginine translocase (Tat) system for translocation and/or membrane insertion. Tat substrates contain an N‐terminal twin‐arginine (SRRxFLK) motif serving as the targeting signal towards the translocon. Many Tat substrates have a system specific chaperone ‐ redox enzyme maturation protein (REMP) – to help mediate final folding and assembly prior to Tat binding. The REMP DmsD strongly interacts with the twin‐arginine motif of the DmsA signal sequence of dimethyl sulfoxide (DMSO) reductase (DmsABC). DmsD adopts monomer, dimer, and unique folding forms that appear under pH control. All alternate DmsD forms retain the ability to bind DmsAL. As well, it is now suggested that DmsD cooperatively binds guanosine‐5′‐triphosphate (GTP), which elicits a dissociative effect on the DmsD to DmsAL interaction. Thus, the primary aim of this study was to analyze DmsD thermal stability when subjected to both GTP association and variance in pH. We have utilized two in vitro protein‐protein interaction techniques of an affinity pull down assay, as well as protein thermal stability measurement via differential scanning fluorimetry (DSF). DSF experiments, yielding melting temperatures as a determinant of the associated thermal stability, showed an increase in DmsD stabilization upon DmsAL binding. Between pH values of 5.0 and 6.0, DmsD demonstrated the least amount of DmsAL release. This pH range also corresponds to a transition in DmsD folding forms. When DmsD was first subjected to GTP binding, subsequent variance in pH decreased melting cooperativity by the appearance of a pretransition peak, but did not affect melting temperature. However, if alteration in pH occurred prior to GTP binding, the pretransition peak was attenuated, and an incremental increase in melting temperature was observed. These findings illustrate that a greater affinity for DmsAL promotes an increase in DmsD thermal stability. As well, pH shift results in formation of a more uniform DmsD population, with subsequent GTP binding permitting an increase in thermal stability. These results support the idea that H + and GTP play roles as molecular regulators in the biochemical pathway of DmsAB protein maturation – Tat system targeting mechanism. Support or Funding Information Research was supported by a Canadian Institutes of Health Research operating grant ( MOP‐49422 ) to RJT.
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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) | 0.001 | 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".