Identification of an ATP-binding cassette cystine import system of Streptococcus mutans and its transcriptional regulation
Bibliographic record
Abstract
The polar amino acid ATP-binding cassette (ABC) transporter, CysBPA, was shown to mediate L-cystine uptake in Streptococcus mutans. Transcriptional analysis enabled identification of a tricistronic operon and the transcriptional start site for cysBPA. Phenotypic characterization of the DeltacysBPA mutant showed a 28% decrease in biofilm biomass and formation of sparse, fragile biofilms when compared to wild-type biofilm grown in a semi-defined minimal medium. While assessing cystine transport, the DeltacysBPA mutant was less efficient at L-cystine uptake and its ability to grow was severely impaired under L-cystine starvation conditions. A substrate competition assay showed that L-cystine uptake by CysBPA was strongly inhibited by DL-cystathionine and L-djenkolic acid and moderately inhibited by S-methyl- L-cysteine and L-cysteine. Through gene expression analysis, the cystine transporter was shown to be up-regulated under cystine starvation and in biofilm-grown cells under acidic conditions. In summary, the CysBPA transporter is involved in cystine transport, growth, and biofilm formation.
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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".