The HPr(Ser) kinase of<i>Streptococcus salivarius</i>: a hexameric bifunctional enzyme controlled by glycolytic intermediates and inorganic phosphate
Bibliographic record
Abstract
Phosphorylation of HPr, the small phosphocarrier protein of the phosphoenolpyruvate:sugar phosphotransferase system, on Ser46 by the HPr(Ser) kinase (HPrK/P) is a vital step in catabolite repression in Gram-positive bacteria. Streptococcus salivarius HPrK/P is reported to be a multimeric protein not regulated by metabolic intermediates. We re-evaluated the molecular mass of S. salivarius HPrK/P using sedimentation equilibrium ultracentrifugation, demonstrated that S. salivarius HPrK/P dephosphorylated HPr(Ser-P) and further characterised the effect of fructose 1,6-bisphosphate and other metabolic intermediates on enzyme activities. The molecular mass of S. salivarius HPrK/P was 201305 Da, suggesting that streptococcal HPrK/P was a hexameric protein. Fructose 1,6-bisphosphate poorly activated streptococcal HPrK/P but protected kinase activity against inhibition by inorganic phosphate and inhibited dephosphorylation of HPr(Ser-P). Phosphoenolpyruvate and 2-phosphoglycerate, but not fructose 1-P, fructose 6-P, and ribulose 1,5-bisphosphate, also protected kinase activity against inhibition by inorganic phosphate. Thus, unlike previous reports, we show that fructose 1,6-bisphosphate and other key glycolytic intermediates played a pivotal role as a modulator of streptococcal HPrK/P activities.
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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) | 0.000 | 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".