Proximity of the Protein Moiety of a GPI-Anchored Protein to the Membrane Surface: A FRET Study
Why this work is in the frame
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Bibliographic record
Abstract
GPI-anchored proteins are ubiquitous on the eukaryotic cell surface, where they are involved in a variety of functions ranging from adhesion to enzymatic catalysis. Indirect evidence suggests that the GPI anchor may hold the protein close to the plasma membrane; however, there is a lack of direct information on the proximity of the protein portion of GPI-anchored proteins to the bilayer surface. The present study uses fluorescence resonance energy transfer (FRET) to address this important problem. The GPI-anchored ectoenzyme placental alkaline phosphatase (PLAP) was purified from a plasma membrane extract of human placental microsomes without the use of butanol. The protein was fluorescently labeled at the N-terminus with 7-(dimethylamino)coumarin-4-acetic acid succinimidyl ester (DMACA-SE) or Oregon Green 488 succinimidyl ester (OG488-SE), and each was reconstituted by detergent dilution into defined lipid bilayer vesicles containing an increasing mole fraction of a fluorescent lipid probe. The fluorescence of the labeled PLAP donors was quenched in a concentration-dependent manner by the lipid acceptors. The energy transfer data were analyzed using an approach that describes FRET between a uniform distribution of donors and acceptors in an infinite plane. The distance of closest approach between the protein moiety of PLAP and the lipid-water interfacial region of the bilayer was estimated to be smaller than 10-14 A. This indicates that the protein portion of PLAP is located very close to the lipid bilayer, possibly resting on the surface. This contact may allow transmission of structural changes from the membrane surface to the protein, which could influence the behavior and catalytic properties of GPI-anchored proteins.
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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 | 0.000 | 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 it