Structural‐functional studies of purified transmembrane segment VI‐VII of the human isoform 1 of the Na <sup>+</sup> /H <sup>+</sup> exchanger
Bibliographic record
Abstract
The Na + /H + exchanger isoform 1 (NHE1) is a ubiquitous pH membrane protein in mammalian cells. NHE1 regulates intracellular pH exchanging one intracellular H + for one extracellular Na + . Though the structure of membrane proteins is highly desirable, expression remains problematic. In this study we expressed and purified transmembrane (TM) VI‐VII of the NHE1 protein. A 49 kDa Maltose‐Binding‐Protein‐TMVI‐VII fusion protein was expressed in E. coli XL1 Blue cells and purified with an Amylose resin. After cleavage with Tobacco Etch Virus, free TM VI‐VII, 6.2 kDa protein was isolated and purified by reverse phase HPLC. The identity was confirmed by Mass Spectroscopy. The structure of 15 N isotopically labeled TM VI‐VII peptide was determined in dodecylphosphocholine micelles using solution‐state 2D and 3D NMR. TM VI‐VII contains a helix‐kink‐helix structure for TM VI with helices between amino acids 229–236 and 239–247. TM VII was a continuous helix from 252–274. The data suggests that the C‐terminal half of TM VI interacts with the N‐terminal half of TM VII. Future studies are further defining the helix‐helix interface between residues of TM VI and TM VII.
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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) | 0.000 | 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".