Solution state characterization of the E. coli inner membrane protein glycerol facilitator
Bibliographic record
Abstract
The Major Intrinsic Proteins are represented in all forms of life; plants, animals, bacteria and recently archaebacteria have all been shown to express at least one member of this superfamily of integral membrane proteins. We have overexpressed the E. coli aquaglyceroporin, glycerol facilitator (GlpF), to use as a model for studying membrane protein structure, folding and stability. Understanding membrane protein folding, stability, and dynamics is required for a molecular explanation of membrane protein function and for the development of interventions for the hundreds of membrane protein folding diseases. X-ray analysis of GlpF crystals shows that the protein exits as a tetramer in the crystallized state [1]. However, preparations of stable aqueous detergent solutions of GlpF in its native oligomeric state have been difficult to make; the protein readily unfolds and forms non-specific aggregates in many detergents. Here, I report the study of the structure and stability of the glycerol facilitator in several detergent solutions by blue native and sodium dodecyl sulphate polyacrylamide gel electrophoresis, circular dichroism, and fluorescence. For the first time, stable protein tetramers were prepared in two different detergent solutions (dodecyl maltoside (DDM) and lyso-myristoyl phosphatidylcholine (LMPC)) at neutral pH. Thermal unfolding experiments show that the protein is slightly more stable in LMPC than in DDM and that the thermal stability of the helical core at 95oC is slightly greater in the former detergent. In addition, tertiary structure unfolds before quaternary and secondary structures in LMPC whereas unfolding is more cooperative in DDM. The high stability of the protein is also evident from the unfolding half-life of 8 days in 8 M urea suggesting that hydrophobic interactions contribute to the stability. The GlpF tetramers are less resistant to acidic conditions; LMPC-solubilized GlpF shows loss of tertiary and quaternary structure by pH 6, while in DDM the tertiary structure is lost by pH 5, however the tetramer remains mostly intact at pH 4. The implications of thermal and chemical stress on the stability of the detergent-solubilized protein and its in vivo folding are 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 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) | 0.000 | 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 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".