Functional investigation of a highly conserved aspartate residue in the anti -cancer drug efflux transport protein MRP1
Bibliographic record
Abstract
Multidrug Resistant Protein 1 (MRP1 or ABCC1) belongs to a subclass of ATP-binding cassette (ABC) transporters that export a wide range of metabolites and xenobiotics across the plasma membrane. Increased expression of MRP1 in cancer cells enhances efflux of many anti-cancer agents, giving rise to multidrug resistant tumours. The purpose of this study was to investigate the function of an aspartate (Asp) amino acid that is highly conserved in all MRP-related proteins by mutating it and determining the consequences of doing so. Asp430 lies at the interface of the cytoplasm and a transmembrane helix in the first membrane-spanning domain of MRP1. Previous studies have shown that when Asp430 is mutated, the protein becomes unstable and is degraded.Because this Asp430 is highly conserved in many MRP-related ABC transporters and because structural homology models of human MRP1 predict that Asp430 is in close proximity to Arg433, we hypothesized that a salt bridge between these two a mino acids could be essential for proper folding and stability of the protein during its biosynthesis. Using site -directed mutagenesis, these two amino acids were interchanged to probe the existence of such an interaction. Thus a double mutant where Asp430 was mutated to Arg, and Arg433 was mutated to Asp was created, and the resultant mutant protein (D430R/R433D) was tested for its ability to be detected in mammalian cells by gel electrophoresis and immunoblotting. Our results show differences between the migration patterns of double and single mutants that are compatible with differences in the glycosylation levels of MRP1. However the fact that D430R and the R433D mutants don’t share the same migration pattern, together with the variation in migration bet ween D430 wild type and Supported by CIHR MOP-10519the double mutant D430R/R433D indicate that the possibility of a salt bridge can be discarded.Supported by CIHR MOP-10519
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| 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".