Strategies for generating soluble and monomeric samples of Ycf1p NBD2
Bibliographic record
Abstract
The yeast cadmium factor 1 protein (Ycf1p) is an ATP-binding cassette (ABC) transporter that is located in the vacuolar membrane and is responsible for transporting glutathione-conjugated metals from the cytoplasm into the vacuole. Ycf1p contains the ABC core structure of two transmembrane domains (TMD1, TMD2) and two nucleotide-binding domains (NBD1, NBD2). As a member of the C-subfamily of ABC proteins (ABCC), Ycf1p also contains an N-terminal extension comprised of an additional TMD (TMD0) and L0 linker. Although high-resolution structures of many ABC transporters have been determined, the NBDs can be at low resolution in cryo-EM maps. Thus, studies of the isolated cytosolic NBDs are crucial for obtaining molecular-level details of the dynamics of these catalytic entities, for example. In this study, we present a scheme for obtaining samples of NBD2 from the yeast cadmium factor 1 protein (Ycf1p) in a soluble, monomeric, and functional form. While production of NBD1 from Ycf1p and other ABC proteins has been accomplished, generating samples of NBD2 from different ABC proteins has been elusive for the most part, particularly for ABCC proteins. We show that NBD2 preparation necessitates minimizing dimerization and aggregation of the protein at multiple steps during the purification, which is accomplished by employing a solubility tag, eliminating nucleotides from the buffers, and limiting the duration of spin concentrating steps. This work lays the foundation for detailed studies of Ycf1p NBD2 and provides an outline for optimizing the generation of samples of NBD2 from other ABC proteins.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".