Altering Heparin Cofactor II at VAL439 (P6) either Impairs Inhibition of Thrombin or Confers Elastase Resistance
Bibliographic record
Abstract
Heparin cofactor II (HCII) is plasma glycoprotein and thrombin inhibitor of the serpin type previously shown to inhibit thrombin in the absence of its N-terminal 74 amino acids, and to be cleaved by neutrophil elastase (NE) at two sites: I66-F67 and V439-G440, the P6-P5 bond of the reactive center loop. We examined the contribution of Val439 to the reaction of HCII with thrombin and NE. Hexahistidine-tagged HCII proteins lacking residues 1-66 (H6delta66HCII) containing either the wild-type Val 439 or one of six substitutions were-expressed in E. coli. The rates of heparin-catalyzed thrombin inhibition of the V439L, C, or R variants were reduced at least 80-fold compared to wild-type H6delta66HCII, while those of the F, S, or W variants were largely unchanged. Following controlled exposure to NE in the presence of heparin, these latter variants retained 3.5- to 4.5-fold more residual anti-thrombin activity than wild-type H6delta66HCII treated in the same manner. This resistance arose due to deflection of NE attack from V439-G440 to secondary sites. The F, S, or W V439 variants exhibited a similar or greater degree of NE resistance when re-expressed as full-length hexahistidine-tagged HCII proteins, suggesting that the I66-F67 NE site is not well recognized in non-glycosylated HCII. Of these full-length variants, the V439F was the most active, exhibiting only a 2-fold reduction in its heparin-catalyzed rate of thrombin inhibition. HCII can therefore be made NE-resistant without severely compromising its capacity to inhibit thrombin.
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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) | 0.002 | 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".