Structure of a dimeric ABC transporter
Bibliographic record
Abstract
Abstract ATP binding cassette (ABC) proteins generally couple ATP hydrolysis to the active transport of solutes across cellular membranes. All ABC proteins contain a core structure of two transmembrane domains (TMD1, TMD2) and two nucleotide binding domains (NBD1, NBD2), and many ABC proteins contain additional domains. Some members of the C subfamily of ABC (ABCC) proteins, such as the multidrug resistant protein 1 (MRP1), contain an N-terminal transmembrane domain (TMD0) and L0 linker that regulate transport activity and cellular trafficking, and mediate interactions with other proteins. Regulation can also be imparted by phosphorylation, proteolytic processing, and/or oligomerization of the proteins. Here we present the structure of yeast cadmium factor 1 (Ycf1p), a homologue of MRP1, in its mature form following cleavage by the yeast protease Pep4p. Remarkably, proteolytically cleaved Ycf1p forms a well-ordered dimer, with some monomeric particles also present in solution. Numerous other ABC proteins have been proposed to form dimers but no high-resolution structures have been reported. The monomeric and dimeric Ycf1p species are differentially phosphorylated at the intrinsically disordered regulatory (R) region, which links NBD1 to TMD2, and possess different ATPase activities indicating that dimerization affects the function of the protein. Protein-protein interactions involving TMD0, the L0 linker, and the R region mediate contacts between Ycf1p protomers in the dimer. In addition, cryo-EM density is observed for lipids at the interface between protomers, which suggests that lipids stabilize the dimer. The Ycf1p dimer structure is consistent with proposed dimerization interfaces of other ABCC dimers, such as MRP1.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".