Determination of the Cd/S Cluster Stoichiometry in <i>Fucus vesiculosus</i> Metallothionein
Bibliographic record
Abstract
The seaweed Fucus vesiculosus is unusual when compared with other algal species, in that it can survive in toxic-metal-contaminated aquatic environments. The metallothionein gene has been identified in F. vesiculosus by Kille and co-workers (Morris, C. A., Nicolaus, B., Sampson, V., Harwood, J. L., and Kille, P. (1999) Biochem. J. 338, 553), which suggests a possible protective mechanism against toxic metals for this species. We report the first detailed study of the metal binding properties of F. vesiculosus metallothionein using UV absorption, circular dichroism (CD), and electrospray mass spectral techniques. The overall metal-to-sulfur ratios of this novel algal protein when bound to divalent cadmium and zinc were determined to be Cd(6)S(16) and Zn(6)S(16), respectively. Mixed Cd/Zn species were also formed when Cd(2+) was added to the Zn-containing Fucus metallothionein. Only one conformation was identified at low pH for the native protein. Analysis of the UV absorption, CD, and ESI-MS spectral data recorded during stepwise, acid-induced demetalation supports a two-domain structure for the protein, with two 3-metal binding sites. The data suggest that one of the domains is significantly less stable than the other, and we tentatively propose from the arrangement of cysteines in the sequence that the two domains are M(3)S(7) and M(3)S(9) (where M = Cd(2+) or Zn(2+)). While the M(3)S(9) cluster is known in the beta clusters of crab, lobster, and mammalian metallothioneins, the M(3)S(7) is a hitherto unknown cluster structure. Metallothionein in F. vesiculosus is thought to act as a protective mechanism against incoming toxic metals. The metal binding studies reported are a putative model for metal binding in vivo.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| 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) | 0.000 | 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".