Cytochrome P450 125 (CYP125) catalyses C26‐hydroxylation to initiate sterol side‐chain degradation in <i>Rhodococcus jostii</i> RHA1
Bibliographic record
Abstract
The cyp125 gene of Rhodococcus jostii RHA1 was previously found to be highly upregulated during growth on cholesterol and the orthologue in Mycobacterium tuberculosis (rv3545c) has been implicated in pathogenesis. Here we show that cyp125 is essential for R. jostii RHA1 to grow on 3-hydroxysterols such as cholesterol, but not on 3-oxo sterol derivatives, and that CYP125 performs an obligate first step in cholesterol degradation. The involvement of cyp125 in sterol side-chain degradation was confirmed by disrupting the homologous gene in Rhodococcus rhodochrous RG32, a strain that selectively degrades the cholesterol side-chain. The RG32 Omega cyp125 mutant failed to transform the side-chain of cholesterol, but degraded that of 5-cholestene-26-oic acid-3beta-ol, a cholesterol catabolite. Spectral analysis revealed that while purified ferric CYP125(RHA1) was < 10% in the low-spin state, cholesterol (K(D)(app) = 0.20 +/- 0.08 microM), 5 alpha-cholestanol (K(D)(app) = 0.15 +/- 0.03 microM) and 4-cholestene-3-one (K(D)(app) = 0.20 +/- 0.03 microM) further reduced the low spin character of the haem iron consistent with substrate binding. Our data indicate that CYP125 is involved in steroid C26-carboxylic acid formation, catalysing the oxidation of C26 either to the corresponding carboxylic acid or to an intermediate state.
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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".