Enhancement of Heparin Cofactor II Anticoagulant Activity

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  • Bauman, Susannah J.
    • School of Medicine
  • Church, Frank C.
    • School of Medicine
Abstract
  • Heparin cofactor II (HCII) is a serpin whose thrombin inhibition activity is accelerated by glycosaminoglycans. We describe the novel properties of a carboxyl-terminal histidine-tagged recombinant HCII (rHCII-CHis(6)). Thrombin inhibition by rHCII-CHis(6) was increased >2-fold at approximately 5 microgram/ml heparin compared with wild-type recombinant HCII (wt-rHCII) at 50-100 microgram/ml heparin. Enhanced activity of rHCII-CHis(6) was reversed by treatment with carboxypeptidase A. We assessed the role of the HCII acidic domain by constructing amino-terminal deletion mutants (Delta1-52, Delta1-68, and Delta1-75) in wt-rHCII and rHCII-CHis(6). Without glycosaminoglycan, unlike wt-rHCII deletion mutants, the rHCII-CHis(6) deletion mutants were less active compared with full-length rHCII-CHis(6). With glycosaminoglycans, Delta1-68 and Delta1-75 rHCIIs were all less active. We assessed the character of the tag by comparing rHCII-CHis(6), rHCII-CAla(6), and rHCII-CLys(6) to wt-rHCII. Only rHCII-CHis(6) had increased activity with heparin, whereas all three mutants have increased heparin binding. We generated a carboxyl-terminal histidine-tagged recombinant antithrombin III to study the tag on another serpin. Interestingly, this mutant antithrombin III had reduced heparin cofactor activity compared with wild-type protein. In a plasma-based assay, the glycosaminoglycan-dependent inhibition of thrombin by rHCII-CHis(6) was significantly greater compared with wt-rHCII. Thus, HCII variants with increased function, such as rHCII-CHis(6), may offer novel reagents for clinical application.
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  • Article
Rights statement
  • In Copyright
Journal title
  • The Journal of Biological Chemistry
Journal volume
  • 274
Journal issue
  • 49
Page start
  • 34556
Page end
  • 34565
Language
  • English
ISSN
  • 0021-9258
  • 1083-351X

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