Role of Cysteine Residues in the NCKX2 Na<sup>+</sup>/Ca<sup>2+</sup>−K<sup>+</sup>Exchanger: Generation of a Functional Cysteine-Free Exchanger
Bibliographic record
Abstract
Cysteine residues play an important role in many proteins, either in enzymatic activity or by mediating inter- or intramolecular interactions. The Na(+)/Ca(2+)-K(+) exchanger plays a critical role in Ca(2+) homeostasis in retinal rod (NCKX1) and cone (NCKX2) photoreceptors by extruding Ca(2+) that enters rod and cone cells via the cGMP-gated channels. NCKX1 and NCKX2 contain five highly conserved cysteine residues. The objectives of this study were threefold: (1) to examine the importance of cysteine residues in NCKX2 protein function; (2) to examine their role in the interaction between NCKX2 and the CNGA subunit of the cGMP-gated channel; and (3) to generate a functional cysteine-free NCKX2 protein. The latter will facilitate structural studies taking advantage of the unique chemistry of the thiol group following insertion of cysteine residues at specific positions in the cysteine-free background. We generated a cysteine-free NCKX2 mutant protein that showed normal protein synthesis and processing and approximately 50% wild-type cation transport function. Cysteine residues were also not critical for the formation of NCKX2 homo-oligmers or NCKX2 hetero-oligomers with the CNGA subunit of the cGMP-gated channel. Our results appear to rule out a critical importance of an intramolecular disulfide linkage in NCKX2 protein synthesis and folding as had been reported before.
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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 | 0.000 |
| 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 | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".