PI-Specific Phospholipase C Cleavage of a Reconstituted GPI-Anchored Protein: Modulation by the Lipid Bilayer
Bibliographic record
Abstract
Release of glycosylphosphatidylinositol- (GPI-) anchored ectoenzymes from the membrane by phosphatidylinositol- (PI-) specific phospholipases may play an important role in modulating the surface expression and function of this group of proteins. To investigate how the properties of the host membrane affect anchor cleavage, porcine lymphocyte ecto-5'-nucleotidase (5'-NTase; EC 3.1.3.5) was purified, reconstituted into lipid bilayer vesicles of various lipids, and cleaved using PI-PLC from Bacillus thuringiensis (Bt-PI-PLC). Bt-PI-PLC activity was highly dependent on the chain length and unsaturation of the constituent phospholipids. Very high rates of cleavage were observed in fluid lipids with a low phase transition temperature (T(m)), in lymphocyte plasma membrane, and in a lipid mixture that formed rafts. Arrhenius plots of the rate of anchor cleavage in various lipids showed a characteristic break at the bilayer T(m), together with a discontinuity close to T(m). The activation energy for GPI anchor cleavage was substantially higher in gel phase bilayers compared to those in the liquid crystalline phase. The addition of cholesterol simultaneously abolished the phase transition and the large difference in cleavage rates observed above and below T(m). Inclusion of GM(1) and GT(1b) (components of lipid rafts) in the bilayer reduced the overall activity, but the pattern of the Arrhenius plots remained unchanged. Both gangliosides had similar effects, suggesting that bilayer surface charge has little influence on PI-PLC activity. Taken together, these results suggest that lipid fluidity and packing are the most important modulators of Bt-PI-PLC activity on GPI anchors.
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How this classification was reachedexpand
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 | 0.000 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".