Role of amino acid position 70 in the binding affinity of p50.1 and p58.1 receptors for HLA-Cw4 molecules
Role of amino acid position 70 in the binding affinity of p50.1 and p58.1 receptors for HLA-Cw4 molecules
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DOI：
10.1002/eji.1830271203
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发表时间：
1997-12-01
影响因子：
5.4
通讯作者：
Moretta, A
中科院分区：
文献类型：
--
作者：
Biassoni, R;Pessino, A;Moretta, A
为了确定人类白细胞抗原-C特异性p58.1/p50.1自然杀伤细胞受体与其配体的结合亲和力的氨基酸位置(S)，我们使用了由任一受体的胞外区与人免疫球蛋白G1Fc部分形成的可溶性融合蛋白。我们发现，可溶性的p50.1(激活)受体与221-CW4转染体结合很弱。相反，可溶性p58.1(抑制性)受体以高亲和力结合。通过定点突变获得的70位氨基酸突变影响了p50.1和p58.1受体的结合亲和力。因此，在p50.1中用苏氨酸取代赖氨酸70(典型的抑制性p58.1分子)导致结合亲和力显著增加，与p58.1分子的结合亲和力相当。另一方面，p58.1上的苏氨酸70被赖氨酸取代几乎取消了与221-CW4细胞的结合。我们目前的数据表明，单个氨基酸的差异极大地影响了p58.1/p50.1对其HLA-C配体的亲和力，并提示第70位可能在自然杀伤细胞受体/主要组织相容性复合体I类相互作用中作为接触位点的作用。
In an attempt to identify the amino acid position(s) of the HLA-C-specific p58.1/p50.1 natural killer cell receptors that determine the binding affinity for their ligand, we used soluble fusion proteins formed by the ectodomain of either receptor and the Fc portion of human IgG1. We show that the soluble p50.1 (activating) receptor binds weakly to 221-Cw4 transfectants. In contrast, the soluble p58.1 (inhibitory) receptor binds with high affinity. A single amino acid mutation at position 70, obtained by site-directed mutagenesis, was found to affect the binding affinity of both the p50.1 and the p58.1 receptors. Thus, substitution in p50.1 of lysine 70 by threonine (typical of the inhibitory p58.1 molecule) resulted in a dramatic increase in binding affinity, comparable to that of the p58.1 molecule. On the other hand, substitution of threonine 70 by lysine in p58.1 almost abolished binding to 221-Cw4 cells. Our present data indicate that a single amino acid difference greatly influences the p58.1/p50.1 affinity for their HLA-C ligand and suggests a possible role of position 70 as a contact site in the natural killer cell receptor/major histocompatibility complex class I interaction.