Functional and structural analysis of transmembrane segment IV of Na+/H+ exchanger of Schizosaccharomyces pombe
Bibliographic record
Abstract
Sod2 is the plasma membrane Na + /H + exchanger of fission yeast S. pombe. It plays an important role in providing salt tolerance to S. pombe by removing excess intracellular sodium (or lithium) in exchange for protons. We examined the role of amino acids residues of TMIV ( 126 FQINFLGSLLIAGCITSTDPVLSALI 152 ) in activity of this protein using alanine scanning mutagenesis, and examining LiCl or NaCl tolerance in Sod2‐deficient S. pombe . We identified two amino acids, T144 and V147, critical for the function of Sod2. The mutations T144A and V147A resulted in a defective sod2 protein that did not confer salt tolerance when reintroduced into to S. pombe . Sod2 protein with other mutations in TMIV, exported either sodium or lithium as efficiently as the wild type Sod2 or had intermediate effects on salt tolerance of S. pombe . When we mutated T144 to aspartic acid, lysine or serine, the mutant proteins were impaired in their ability to allow growth in both lithium and sodium containing media, comparable to the knock out sod2 yeast (sod2::ura4). Western blot analysis showed that mutants T144A and V147A were expressed at comparable levels as the wild type sod2. To determine the structure of TMIV, we expressed and purified TMIV as a fusion protein with maltose binding protein. The TMIV peptide was released by cleaving the fusion protein with tobacco etch virus and re‐purified by HPLC. The structure is being determined by NMR. Supported by Natural Sciences and Engineering Research Council of Canada
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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".