Amphipol-facilitated elucidation of the functional tetrameric complex of full-length cytochrome P450 CYP2B4 and NADPH-cytochrome P450 oxidoreductase
Bibliographic record
Abstract
Interactions of membrane-bound mammalian cytochromes P450 (CYPs) with NADPH-cytochrome P450 oxidoreductase (POR), which are required for metabolism of xenobiotics, are facilitated by membrane lipids. A variety of membrane mimetics, such as phospholipid liposomes and nanodiscs, have been used to simulate the membrane to form catalytically active CYP:POR complexes. However, the exact mechanism(s) of these interactions are unclear because of the absence of structural information of full-length mammalian CYP:POR complexes in membranes. Herein, we report the use of amphipols (APols) to form a fully functional, soluble, homogeneous preparation of full-length CYP:POR complexes amenable to biochemical and structural study. Incorporation of CYP2B4 and POR into APols resulted in a CYP2B4:POR complex with a stoichiometry of 1:1, which was fully functional in demethylating benzphetamine at a turnover rate of 37.7 ± 2.2 min −1 , with a coupling efficiency of 40%. Interestingly, the stable complex had a molecular weight (M w ) of 338 ± 22 kDa determined by multiangle light scattering, suggestive of a tetrameric complex of 2CYP2B4:2POR embedded in one APol nanoparticle. Moreover, negative stain electron microscopy (EM) validated the homogeneity of the complex and allowed us to generate a three-dimensional EM map and model consistent with the tetramer observed in solution. This first report of the full-length mammalian CYP:POR complex by transmission EM not only reveals the architecture that facilitates electron transfer but also highlights a potential use of APols in biochemical and structural studies of functional CYP complexes with redox partners.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".