Probing Heteromultivalent Protein–Glycosphingolipid Interactions using Native Mass Spectrometry and Nanodiscs
Bibliographic record
Abstract
Interactions between glycosphingolipids (GSLs) on the surfaces of cells and glycan-binding proteins (GBPs) mediate a wide variety of essential and pathological processes. Despite the biological importance of these interactions, the GSL ligands of most GBPs remain to be identified and the mechanisms controlling recognition of GSLs are incompletely understood. Recently, it was suggested that, when present together with high affinity ligands, low affinity GSL ligands can contribute significantly to the binding of GBPs with multiple binding sites through a process called heteromultivalent binding. Here, with goal of directly establishing the existence of heteromultivalent GSL interactions and elucidating the mechanism underlying their formation, we investigated cholera toxin B subunit homopentamer (CTB 5 ) binding to ganglioside mixtures in model membranes (nanodiscs) using native mass spectrometry (MS) and competitive ligand binding. Electrospray ionization (ESI)-MS analysis revealed that the presence of the high affinity ligand GM1 (at substoichiometric amounts relative to binding sites) in the nanodisc promotes GD1b binding to CTB 5; no GD1b binding was detected in the absence of GM1. No direct ESI-MS evidence of CTB 5 binding to the other five gangliosides tested, alone or present together with GM1 in the nanodiscs, was observed. Affinity measurements, carried out using the proxy ligand ESI-MS binding assay, confirmed that GD1b binding to CTB 5 is dramatically enhanced (>1000-times higher affinity compared to the GD1b oligosaccharide affinity) when present with GM1. NDs containing GM1 and GM2, GD1a, or GT1b also exhibited enhanced CTB 5 binding, however, the effect was smaller. The results of molecular dynamics simulations performed on ganglioside-containing nanodiscs suggest that the participation of low affinity ligands in heteromultivalent binding with GM1 may be regulated by the positions of the internal Gal-linked Neu5Ac residues of the gangliosides relative to the membrane surface.
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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".