Biochemistry and physiology of NhaP-type antiporters in Vibrio cholerae
Bibliographic record
Abstract
Antiporters that exchange alkali cations (Na+ or K+) for protons play an important role in the physiology of all known bacterial species. They are involved in regulating intracellular pH and maintaining cellular volume as well as the formation of a chemical Na+ gradient across the membrane, which is important to many bacteria as an energy source for processes such as accumulation of substrates, ATP synthesis, and flagellar rotation. Another important role of cation/proton antiporters is homeostasis of intracellular cation content. The situation of a thermodynamic equilibrium of Na+ or K+ on the membrane would result in toxic intracellular levels of these cations, so bacteria have cation/proton antiporters, which expel excess of alkali cations at the expense of the proton motive force. Of many antiporters described to date, the NhaP-type family is one of the most interesting groups. Its members collectively demonstrate a great diversity of their features. There are three antiporters of NhaP type encoded in the genome of the dangerous human pathogen, Vibrio cholerae. Phenotype analysis of engineered chromosomal VcnhaP1, VcnhaP2 and VcnhaP3 deletion mutants has proven the three NhaP paralogues to be essential for V. cholerae growth at low pH in the presence of high or low concentrations of K+. Genes encoding Vc-NhaP1-3 were cloned and antiporters expressed in their functional form in an antiporter-less strains of Escherichia coli. Although initially annotated as Na+/H+ antiporters, when assayed in everted membrane vesicles, all three isoforms of Vc-NhaP were shown to be K+/H+ antiporters with only limited ability to Na+/H+ antiport. None of three proteins was able to mediate Li+/H+ exchange. Overall, the three antiporters differed in their biochemical profiles, predicted topology, and their phenotypic manifestations.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 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".