Direct Fusion of the CAII Carbonic Anhydrase to the AE1 Cl‐/HCO3‐ Exchanger
Why this work is in the frame
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Bibliographic record
Abstract
Some bicarbonate transporters bind to carbonic anhydrases (CA) to enhance their transport activities. Carbonic anhydrases catalyze the reversible conversion of CO 2 to HCO 3 − + H + and thus produce or consume the substrate of HCO 3 − transport. To further understand the physiological role of the CA/bicarbonate transporter interaction, we investigated the transport activity of the human Cl − /HCO 3 − exchanger isoform, AE1, by fusing CAII to its C‐terminal region (AE1.CAII). As a control, AE1 was also fused to the catalytically inactive CAII mutant, V143Y, to generate AE1.CAIIV143Y. AE1 alone and the two fused proteins were expressed by transient transfection of HEK293 cells. Anion exchange activity, monitored from the rates of intracellular pH (pH i ) change upon shifting extracellular Cl − from 140 mM to 0 mM and back, was determined by measuring the fluorescence of the pH indicator dye, 2′,7′‐bis (2‐carboxylethyl)‐5(6)‐carboxyfluorescein (BCECF). The anion transport activity of AE1.CAII, normalized for AE1 expression level, was 119% ± 15% of cells transfected with AE1 alone. Interestingly, the transport activity of AE1.CAIIV143Y was markedly reduced (47% ± 10%) compared to AE1 alone. The reduction of activity of the AE1.CAIIV143Y fusion relative to AE1 alone suggests that the fusion compromises AE1 folding or activity. We conclude that catalytically active CAII tethered to the cytosolic surface of AE1 activates Cl − /HCO 3 − exchange activity.
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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) | 0.000 | 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 it