Metalation Kinetics of the Human α‐Metallothionein 1a Fragment Is Dependent on the Fluxional Structure of the apo‐Protein
Bibliographic record
Abstract
Mammalian metallothioneins are cysteine rich metal-binding proteins comprising, when fully metalated, two metal-binding domains: the α-domain binds with M4(II)S(Cys)11 stoichiometry and the β domain binds as M3(II)S(Cys)9 stoichiometry. While the fully metalated species have been widely studied, the metalation of the apoprotein is poorly understood. Key to a description of the metalation pathway(s) is the initial conformation of the apoprotein and the arrangement of the metal-coordinating cysteines prior to metalation. We report the effect of the ill-defined, globular structure of apoMT on metalation rates. In order to overcome the experimental limitations inherent in structural determinations of a fluxional protein we used a detailed analysis of the apo-α-metallothionein conformation based on the differential rate of cysteine modification with benzoquinone. The ESI mass spectral data show the presence of two distinct conformational families: one a folded conformational family at neutral pH and a second an unfolded family of conformations at low pH. The Cd(II) metalation properties of these two conformationally distinct families were studied using stopped-flow kinetics. Surprisingly, the unfolded apoprotein metalated significantly slower than the folded apoprotein, a result interpreted as being due to the longer time required to fold into the cluster structure when the fourth Cd(II) binds. These results provide the first evidence for the role of the structure of the apo-αMT in the metalation reaction pathways and show that cysteine modification coupled with ESI-MS can be used to probe structure in cysteine-rich proteins.
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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 | 0.001 | 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 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".