Transcriptional and translational analysis of the ccaR gene from Streptomyces clavuligerus
Bibliographic record
Abstract
CcaR is a positive-acting transcriptional regulator involved in cephamycin C and clavulanic acid biosynthesis in Streptomyces clavuligerus. Previous sequence analyses of the ccaR gene revealed two possible start codons, an ATG, and a GTG located in-frame 18 bp downstream of the ATG. To determine the true start codon, ccaR was expressed, either from the GTG or ATG codon, in Escherichia coli. A protein product was only obtained from the ATG construct. Similarly, ccaR constructs originating from ATG or GTG and designed for expression from a glycerol-regulated promoter in Streptomyces species were prepared and used to complement a S. clavuligerus ccaR mutant. Bioassays showed that only the ATG construct could complement the ccaR mutant to restore cephamycin C production, and Western analysis confirmed the presence of CcaR in the mutant complemented with the ATG construct only. To ensure that expression of ccaR from its native promoter also initiated at the ATG rather than GTG, a conservative point mutation was introduced into ccaR, converting the GTG to GTC. The GTC construct still fully complemented a ccaR mutant, confirming that ATG is the true start codon. Inspection of the region upstream of ccaR by S1 nuclease protection and primer extension analyses indicated the presence of two transcript start points that mapped to residues located 74 and 173 bp upstream of the ATG codon.
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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".