Proteomic assessment of an established technique for carboxysome enrichment from <i>Synechococcus</i> PCC7942
Bibliographic record
Abstract
Carboxysomes are protein-bound, polyhedral microbodies within cyanobacteria, containing the key enzyme for photosynthetic CO 2 fixation, ribulose-1,5-bisphosphate carboxylaseoxygenase (Rubisco). Sequencing of cyanobacterial genomes has revealed that cyanobacteria possess one or other of two types of carboxysomes. Cyanobacteria containing form 1A Rubisco possess α-carboxysomes, while those with form 1B Rubisco possess β-carboxysomes. Given the central importance of carboxysomes in the CO 2 -concentrating mechanism of cyanobacteria, understanding the nature and composition of these structures is of considerable importance. In an effort to develop techniques for the characterization of the structure of β-carboxysomes, particularly the outer protein shell, we have undertaken a proteomic assessment of the PercollMg 2+ carboxysome enrichment technique using the freshwater cyanobacterium Synechococcus sp. PCC7942. Both matrix-assisted laser desorptionionization time of flight mass spectrometry (MALDI-TOF MS) and multidimensional protein identification technology (MuDPIT) methods were used to determine the protein content of a novel carboxysome-rich fraction. A total of 17 proteins were identified using MALDI-TOF MS from enriched carboxysome preparations, while 122 proteins were identified using MuDPIT analysis on the same material. The carboxysomal protein CcmM was identified by MALDI-TOF MS as two distinct proteins of 38 and 58 kDa. The only other carboxysomal proteins identified were the large and small subunits of Rubisco (RbcL and RbcS). Reasons for the lack of evidence for the expected full complement of carboxysomal proteins and future directions are discussed.Key words: CO 2 -concentrating mechanism, cyanobacteria, carboxysomes, proteomics.
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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".