Functional dissection of Ctr4 and Ctr5 amino-terminal regions reveals motifs with redundant roles in copper transport
Bibliographic record
Abstract
Copper uptake in the fission yeast Schizosaccharomyces pombe is carried out by a heteromeric complex formed by two proteins, Ctr4 and Ctr5. In this study, a stable expression system using integrative plasmids was developed to investigate the respective roles of Ctr4 and Ctr5 in copper transport. It was shown that expression of full-length Ctr4 or truncated Ctr4 containing residues 106-289 was required for localization of Ctr5 to the plasma membrane. Likewise, when the full-length Ctr5 or truncated Ctr5 from residues 44-173 was co-expressed with Ctr4, this protein was visualized at the periphery of the cell. To determine the importance of the Mets motifs (consisting of five methionines arranged as Met-X2-Met-X-Met, where X is any amino acid) of Ctr4 and Ctr5 in the heteroprotein complex, we co-expressed Ctr5 lacking the Mets motif and Cys-X-Met-X-Met sequence with wild-type Ctr4 or its mutant derivatives. Conversely, Ctr4 lacking the Mets motif and Met(122) was expressed with wild-type Ctr5 or its mutant derivatives. These experiments revealed that the five Mets motifs of Ctr4 and the Ctr4 residue Met(122) have equally important roles in copper assimilation. Furthermore, the two partially overlapping Mets motifs and the Cys-X-Met-X-Met sequence in Ctr5 have redundant functions in copper transport, with the latter sequence making a greater contribution than the former. Together, the data reveal that co-expression of both Ctr4 and Ctr5 is necessary for the proper function and localization of the heteroprotein complex to the plasma membrane. Once on the cell surface, the N-terminal regions of Ctr4 and Ctr5 can function independently to transport copper; however, the greatest efficiency is achieved when both N termini are present.
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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".