Hayakawa Yumiko, Hirashima Yutaka, Kurimoto Masanori, Hayashi Nakamasa, Hamada Hideo, Kuwayama Naoya, Endo Shunro
Department of Neurosurgery, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Japan.
FEBS Lett. 2002 Jul 3;522(1-3):147-50. doi: 10.1016/s0014-5793(02)02930-7.
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.
肝素辅因子II（HCII）对凝血酶的抑制作用可被肝素或硫酸皮肤素加速1000倍。为了研究HCII A螺旋的碱性残基对这种激活作用的贡献，我们通过定点诱变构建了氨基酸替代物（K101Q、R103L和R106L）。与野生型重组HCII相比，K101Q大大降低了肝素辅因子活性，并且需要超过10倍浓度的硫酸皮肤素才能加速凝血酶抑制。硫酸皮肤素对R106L的凝血酶抑制作用没有明显的刺激作用。这些结果证明，HCII A螺旋的碱性残基（Lys(101)和Arg(106)）对于肝素或硫酸皮肤素加速凝血酶抑制是必需的。
