Expression of<i>ccaR</i>, Encoding the Positive Activator of Cephamycin C and Clavulanic Acid Production in<i>Streptomyces clavuligerus</i>, Is Dependent on<i>bldG</i>
Bibliographic record
Abstract
In Streptomyces coelicolor, bldG encodes a putative anti-anti-sigma factor that regulates both aerial hypha formation and antibiotic production, and a downstream transcriptionally linked open reading frame (orf3) encodes a putative anti-sigma factor protein. A cloned DNA fragment from Streptomyces clavuligerus contained an open reading frame that encoded a protein showing 92% identity to the S. coelicolor BldG protein and 91% identity to the BldG ortholog in Streptomyces avermitilis. Sequencing of the region downstream of bldG in S. clavuligerus revealed the presence of an open reading frame encoding a protein showing 72 and 69% identity to the ORF3 proteins in S. coelicolor and S. avermitilis, respectively. Northern analysis indicated that, as in S. coelicolor, the S. clavuligerus bldG gene is expressed as both a monocistronic and a polycistronic transcript, the latter including the downstream orf3 gene. High-resolution S1 nuclease mapping of S. clavuligerus bldG transcripts revealed the presence of three bldG-specific promoters, and analysis of expression of a bldGp-egfp reporter indicated that the bldG promoter is active at various stages of development and in both substrate and aerial hyphae. A bldG null mutant was defective in both morphological differentiation and in the production of secondary metabolites, such as cephamycin C, clavulanic acid, and the 5S clavams. This inability to produce cephamycin C and clavulanic acid was due to the absence of the CcaR transcriptional regulator, which controls the expression of biosynthetic genes for both secondary metabolites as well as the expression of a second regulator of clavulanic acid biosynthesis, ClaR. This makes bldG the first regulatory protein identified in S. clavuligerus that functions upstream of CcaR and ClaR in a regulatory cascade to control secondary metabolite production.
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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".