Contribution of basic residues of the A helix of heparin cofactor II to heparin- or dermatan sulfate-mediated thrombin inhibition.
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 (Lys(101) and Arg(106)) are necessary for heparin- or dermatan sulfate-accelerated thrombin inhibition.
Hayakawa
Yumiko
Y
Department of Neurosurgery, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Japan. hayakawa@ms.toyama-mpu.ac.jp
Hirashima
Yutaka
Y
Kurimoto
Masanori
M
Hayashi
Nakamasa
N
Hamada
Hideo
H
Kuwayama
Naoya
N
Endo
Shunro
S
D000595:Amino Acid Sequence; D024361:Amino Acids, Basic / Q000235:genetics / Q000378:metabolism*; D001667:Binding, Competitive; D003871:Dermatan Sulfate / Q000494:pharmacology*; D014644:Genetic Variation; D006493:Heparin / Q000494:pharmacology*; D015844:Heparin Cofactor II / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000138:chemical synthesis; D012685:Sepharose / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000378:metabolism*; D013917:Thrombin / Q000037:antagonists & inhibitors*
D024361:Amino Acids, Basic; D010455:Peptides; D015842:Serine Proteinase Inhibitors; D003871:Dermatan Sulfate; D015844:Heparin Cofactor II; D006493:Heparin; D012685:Sepharose; D013917:Thrombin