He X, Shen L, Villoutreix B O, Dahlbäck B
Department of Clinical Chemistry, Wallenberg Laboratories, Lund University, University Hospital MAS, S-205 02 Malmö, Sweden.
J Biol Chem. 1998 Oct 16;273(42):27449-58. doi: 10.1074/jbc.273.42.27449.
Human protein S (PS) potentiates the anticoagulant activity of human but not bovine activated protein C (APC), whereas bovine PS is a cofactor to APC from both species. The structural requirements for the specificity of the APC cofactor function of human PS are located in its thrombin-sensitive region (TSR) and the first epidermal growth factor (EGF1)-like module. To elucidate which residues in these two modules determine the specificity of the APC cofactor activity, 41 human PS mutants were expressed. All mutants were cofactors to human APC and some also to bovine APC. Residues in TSR (positions 49 and 52) and EGF1 (residues 97 and 106) together determined the specificity of the APC cofactor function, whereas substitution of individual residues did not change specificity. Bovine PS, and mutants expressing cofactor activity to bovine APC, stimulated phospholipid binding of bovine APC. In contrast, human PS and mutants lacking cofactor activity to bovine APC failed to support binding of bovine APC to phospholipids. These data indicate that residues in TSR and EGF1 cause the specificity of the APC cofactor activity and support the concept that key residues in these two modules interact with APC on the phospholipid surface.
人蛋白S（PS）可增强人活化蛋白C（APC）的抗凝活性，但对牛活化蛋白C无此作用，而牛PS是这两个物种来源的APC的辅因子。人PS的APC辅因子功能特异性的结构要求位于其凝血酶敏感区（TSR）和第一个表皮生长因子（EGF1）样结构域。为了阐明这两个结构域中的哪些残基决定了APC辅因子活性的特异性，我们表达了41种人PS突变体。所有突变体都是人APC的辅因子，有些也是牛APC的辅因子。TSR中的残基（第49和52位）和EGF1中的残基（第97和106位）共同决定了APC辅因子功能的特异性，而单个残基的替换不会改变特异性。牛PS以及对牛APC具有辅因子活性的突变体刺激了牛APC与磷脂的结合。相反，人PS以及对牛APC缺乏辅因子活性的突变体不能支持牛APC与磷脂的结合。这些数据表明，TSR和EGF1中的残基导致了APC辅因子活性的特异性，并支持了这两个结构域中的关键残基在磷脂表面与APC相互作用的概念。
