<sup>15</sup>N−<sup>1</sup>H HSQC NMR Evidence for Distinct Specificity of Two Active Sites in <i>Escherichia coli</i> Glyoxalase I
Bibliographic record
Abstract
Much remains to be elucidated concerning the selectivity mechanism of supposedly identical active sites in oligomeric proteins. Glyoxalase I (GlxI) catalyzes the glutathione-dependent conversion of 2-oxoaldehydes to S-2-hydroxyacylglutathione derivatives. The E. coli GlxI is a Ni(2+)/Co(2+)-activated homodimeric protein containing two symmetric, and dually metallated active sites as characterized by X-ray structure determination. Nevertheless, kinetics and isothermal titration calorimetric (ITC) studies indicate that dimeric GlxI binds to metal ions in a ratio of 1:1 (one metal ion/one dimer) [ Clugston , S. L. , Yajima , R. , and Honek , J. F. ( 2004 ) Biochem. J. 377 , 309 - 316 ]. In the current study, we provide spectroscopic evidence for the nonequivalent metallation of GlxI by use of (15)N-(1)H HSQC NMR titration experiments. (15)N-(1)H HSQC NMR spectra reveal that the local conformations of the two active sites in homodimeric GlxI are initially asymmetric in the apo-form, resulting in functional differentiation, wherein only one active site binds to the Ni(2+) ion, and another active site is observed to be more selective for a potent inhibitor. The current results enhance our understanding of GlxI structure-function relationships and provide a potential new strategy for the development of small molecule inhibitors for this enzyme system.
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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) | 0.003 | 0.001 |
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".