Inositol monophosphate phosphatase genes of Mycobacterium tuberculosis
Bibliographic record
Abstract
BACKGROUND: Mycobacteria use inositol in phosphatidylinositol, for anchoring lipoarabinomannan (LAM), lipomannan (LM) and phosphatidylinosotol mannosides (PIMs) in the cell envelope, and for the production of mycothiol, which maintains the redox balance of the cell. Inositol is synthesized by conversion of glucose-6-phosphate to inositol-1-phosphate, followed by dephosphorylation by inositol monophosphate phosphatases (IMPases) to form myo-inositol. To gain insight into how Mycobacterium tuberculosis synthesises inositol we carried out genetic analysis of the four IMPase homologues that are present in the Mycobacterium tuberculosis genome. RESULTS: Mutants lacking either impA (Rv1604) or suhB (Rv2701c) were isolated in the absence of exogenous inositol, and no differences in levels of PIMs, LM, LAM or mycothiol were observed. Mutagenesis of cysQ (Rv2131c) was initially unsuccessful, but was possible when a porin-like gene of Mycobacterium smegmatis was expressed, and also by gene switching in the merodiploid strain. In contrast, we could only obtain mutations in impC (Rv3137) when a second functional copy was provided in trans, even when exogenous inositol was provided. Experiments to obtain a mutant in the presence of a second copy of impC containing an active-site mutation, in the presence of porin-like gene of M. smegmatis, or in the absence of inositol 1-phosphate synthase activity, were also unsuccessful. We showed that all four genes are expressed, although at different levels, and levels of inositol phosphatase activity did not fall significantly in any of the mutants obtained. CONCLUSIONS: We have shown that neither impA, suhB nor cysQ is solely responsible for inositol synthesis. In contrast, we show that impC is essential for mycobacterial growth under the conditions we used, and suggest it may be required in the early stages of mycothiol synthesis.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.000 |
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".