Contribution of basic residues of the A helix of heparin cofactor II to heparin‐ or dermatan sulfate‐mediated thrombin inhibition

[摘要]

Inhibition of thrombin by heparin cofactor II (HCII) is accelerated 1000-fold by heparin or dermatan sulfate. To investigate the contribution of basic residues of the A helix of HCII to this activation, we constructed amino acid substitutions (K101Q, R103L, and R106L) by site-directed mutagenesis. K101Q greatly reduced heparin cofactor activity and required a more than 10-fold higher concentration of dermatan sulfate to accelerate thrombin inhibition compared with wild-type recombinant HCII. Thrombin inhibition by R106L was not significantly stimulated by dermatan sulfate. These results provide evidence that basic residues of the A helix of HCII (Lys¹⁰¹ and Arg¹⁰⁶) are necessary for heparin- or dermatan sulfate-accelerated thrombin inhibition.

[学科分类] 生物化学/生物物理

[关键词] Serpin;Heparin cofactor II;Heparin;Dermatan sulfate;Thrombin;HCII;heparin cofactor II;rHCII;recombinant heparin cofactor II;serpin;serine protease inhibitor;AT;antithrombin;GAG;glycosaminoglycan