Secondary Structure and Oligomerization of the <i>E. coli</i> Glycerol Facilitator
Bibliographic record
Abstract
The Major Intrinsic Proteins are found throughout the bacterial, plant, and animal kingdoms and are responsible for the rapid transport of water and other small, polar solutes across membranes. The superfamily includes the aquaporins, the aquaglyceroporins, and the glycerol facilitators. We have overexpressed and purified the Escherichia coli inner membrane glycerol facilitator. Approximately 7.5 mg of 95% pure protein is obtained from 1 L of Escherichia coli cells using immobilized metal affinity chromatography. Well-resolved matrix-assisted laser desorption ionization mass spectra were obtained by solubilization of the protein in octyl-beta-D-glucopyranoside (M(r) = 33 650.3; error approximately 0.4%). The recombinant glycerol facilitator is inserted into the bacterial inner membrane, is functional, and is inhibited by HgCl(2). Polyacrylamide gel electrophoresis suggests that the facilitator is predominantly monomeric when solubilized with dodecyl-beta-D-maltoside, octyl-beta-D-glucopyranoside, and sodium dodecyl sulfate, but that it self-associates, forming soluble oligomers when urea is used during extraction. Similar oligomeric species are demonstrated to exist in the bacterial membrane by chemical cross-linking experiments. Circular dichroism analysis shows that the protein is predominantly alpha-helical. Helix content is significantly higher in protein prepared in the absence of urea (42-55%) than in its presence (32%). A possible role for the facilitator oligomers in interactions with, and regulation of, the glycerol kinase is discussed.
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 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".