Properties of CsnR, the Transcriptional Repressor of the Chitosanase Gene, <i>csnA</i> , of Streptomyces lividans
Bibliographic record
Abstract
A palindromic sequence is present in the intergenic region preceding the chitosanase gene csnA (SSPG_06922) of Streptomyces lividans TK24. This sequence was also found in front of putative chitosanase genes in several other actinomycete genomes and upstream genes encoding putative transcriptional regulators of the ROK family, including csnR (SSPG_04872) in S. lividans. The latter was examined as a possible transcriptional regulator (CsnR) of chitosanase gene expression. In vitro, purified CsnR bound strongly to the palindromic sequences of the csnA and csnR genes (equilibrium dissociation constant [K(D)] = 0.032 and 0.040 nM, respectively). Binding was impaired in the presence of chitosan oligosaccharides and d-glucosamine, and chitosan dimer was found to be the best effector, as determined by an equilibrium competition experiment and 50% inhibitory concentration (IC(50)) determination, while glucose, N-acetyl-glucosamine, and galactosamine had no effect. In vivo, comparison of the S. lividans wild type and ΔCsnR strains using β-lactamase reporter genes showed that CsnR represses the expression of csnA and of its own gene, which was confirmed by quantitative PCR (qPCR). CsnR is localized at the beginning of a gene cluster, possibly an operon, the organization of which is conserved through many actinomycete genomes. The CsnR-mediated chitosanase regulation mechanism seems to be widespread among actinomycetes.
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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) | 0.001 | 0.001 |
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".