NMR Spectroscopic Analysis Reveals Extensive Binding Interactions of Complex Xyloglucan Oligosaccharides with the <i>Cellvibrio japonicus</i> Glycoside Hydrolase Family 31 α‐Xylosidase
Bibliographic record
Abstract
The study of the interaction of glycoside hydrolases with their substrates is fundamental to diverse applications in medicine, food and feed production, and biomass-resource utilization. Recent molecular modeling of the α-xylosidase CjXyl31A from the soil saprophyte Cellvibrio japonicus, together with protein crystallography and enzyme-kinetic analysis, has suggested that an appended PA14 protein domain, unique among glycoside hydrolase family 31 members, may confer specificity for large oligosaccharide fragments of the ubiquitous plant polysaccharide xyloglucan (J. Larsbrink, A. Izumi, F.M. Ibatullin, A. Nakhai, H.J. Gilbert, G.J. Davies, H. Brumer, Biochem. J. 2011, 436, 567-580). In the present study, a combination of NMR spectroscopic techniques, including saturation transfer difference (STD) and transfer NOE (TR-NOE) spectroscopy, was used to reveal extensive interactions between CjXyl31A active-site variants and xyloglucan hexa- and heptasaccharides. The data specifically indicate that the enzyme recognizes the entire cello-tetraosyl backbone of the substrate and product in positive enzyme subsites and makes further significant interactions with internal pendant α-(1→6)-linked xylosyl units. As such, the present analysis provides an important rationalization of previous kinetic data on CjXyl31A and unique insight into the role of the PA14 domain, which was not otherwise obtainable by protein crystallography.
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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) | 0.001 | 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".