Instability of Superoxide Dismutase 1 of Drosophila in Mutants Deficient for Its Cognate Copper Chaperone
Bibliographic record
Abstract
Copper,zinc superoxide dismutase (SOD1) in mammals is activated principally via a copper chaperone (CCS) and to a lesser degree by a CCS-independent pathway of unknown nature. In this study, we have characterized the requirement for CCS in activating SOD1 from Drosophila. A CCS-null mutant (Ccs(n)(29)(E)) of Drosophila was created and found to phenotypically resemble Drosophila SOD1-null mutants in terms of reduced adult life span, hypersensitivity to oxidative stress, and loss of cytosolic aconitase activity. However, the phenotypes of CCS-null flies were less severe, consistent with some CCS-independent activation of Drosophila SOD1 (dSOD1). Yet SOD1 activity was not detectable in Ccs(n)(29)(E) flies, due largely to a striking loss of SOD1 protein. In contrast, human SOD1 expressed in CCS-null flies is robustly active and rescues the deficits in adult life span and sensitivity to oxidative stress. The dependence of dSOD1 on CCS was also observed in a yeast expression system where the dSOD1 polypeptide exhibited unusual instability in CCS-null (ccs1Delta) yeast. The residual dSOD1 polypeptide in ccs1Delta yeast was nevertheless active, consistent with CCS-independent activation. Stability of dSOD1 in ccs1Delta cells was readily restored by expression of either yeast or Drosophila CCS, and this required copper insertion into the enzyme. The yeast expression system also revealed some species specificity for CCS. Yeast SOD1 exhibits preference for yeast CCS over Drosophila CCS, whereas dSOD1 is fully activated with either CCS molecule. Such variation in mechanisms of copper activation of SOD1 could reflect evolutionary responses to unique oxygen and/or copper environments faced by divergent species.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".