Functional Characterization and Assembly Studies of Carboxysomes in <i>Halothiobacillus neapolitanus</i>
Bibliographic record
Abstract
Functional characterization and assembly studies of carboxysomes in Halothiobacillus neapolitanus were pursued in order to understand the roles of carboxysomes in the carbon metabolism in H. neapolitanus and the assembly of carboxysomes in vitro and in vivo. Previously, a low abundance H. neapolitanus carboxysomal protein, CsoSCA was identified as a novel carboxysomal shell-bound carbonic anhydrase. The enzyme is thought to dehydrate the cytosolic bicarbonate to CO2, the substrate of the RuBisCO packaged within the carboxysome [14, 21]. In this study, the carboxysomal shell was identified as a diffusion barrier for CO2 and O2 molecules. The shell-bound CsoSCA protein facilitates the diffusion of CO2 molecules into the carboxysomes and enhances the catalytic efficiency of the encapsulated RuBisCO. The discrimination between CO2 and O2 molecules by the shell makes the sequestered RuBisCO favor the carboxylation over the oxygenation reaction at low O2 concentration. A second substrate, ribulose 1,5-bisphosphate (RuBP), and the carboxylation reaction product, 3-phosphoglycerate (PGA), are negatively charged molecules and need to be transported into and out of the carboxysomes. Bioinformatics analysis of CsoS2 protein revealed that CsoS2 protein carries a positive charge in the cytoplasm. The protein may interact with these negatively charged molecules due to its high isoelectric point (approximately 9.2). Full length CsoS2 and an N-terminally truncated CsoS2 protein were expressed in E.coli to permit three dimensional structure determination. A sequential peptide affinity (SPA) tag was added at the C-terminus of CsoS2 protein to determine its location in the carboxysomes and trap the intermediates of in vitro carboxysome shell assembly. Finally, the cso operon was heterologously expressed in E. coli and some functional carboxysome-like structures were isolated and analyzed. The assembly of carboxysome-like structures in E. coli will guide the in vitro assembly of carboxysomes with recombinant carboxysomal proteins.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".