Mutation of a ligand binding domain of beta 3 integrin. Integral role of oxygenated residues in alpha IIb beta 3 (GPIIb-IIIa) receptor function.
Mutation of a ligand binding domain of beta 3 integrin. Integral role of oxygenated residues in alpha IIb beta 3 (GPIIb-IIIa) receptor function.
复制标题
DOI：
--
复制
发表时间：
1994-08
期刊：
影响因子：
--
通讯作者：
M. Bajt;J. Loftus
中科院分区：
文献类型：
--
作者：
M. Bajt;J. Loftus
β 3中的单个氨基酸取代（Asp 119-> Tyr）消除β 3整联蛋白的配体结合功能，并改变血小板整联蛋白α IIb β 3（GPIIb-IIIa）的二价阳离子构象。该天冬氨酸残基位于保守的含氧残基簇内，其可以提供用于二价阳离子配位的配体。为了将功能分配给该组中的其他含氧残基（Ser 121、Ser 123、Asp 126、Asp 127和Ser 130），β 3中的这些氨基酸中的每一个被丙氨酸单独取代。这些氨基酸取代都没有改变异源二聚体的形成或表面表达。然而，取代对受体功能有不同的影响。在Asp 119或Ser 121位置的取代产生受体功能的完全丧失。表达这些突变体的细胞不能粘附于纤维蛋白原，不能结合活化非依赖性配体模拟肽，并且在受体活化后不能结合配体模拟mAb PAC 1。类似地，表达在Ser 123处具有取代的β 3的细胞也不能粘附纤维蛋白原，并且不结合RGD肽或mAb PAC 1。这些细胞确实保留了结合α IIb β 3特异性、高亲和力肽模拟物的能力，但占据没有诱导野生型受体占据后观察到的从静息状态到活化状态的构象变化。Asp 126、Asp 127或Ser 130位的取代对配体结合功能没有影响。这些数据表明，Asp 119，沿着Ser 121和Ser 123，在α IIb β 3的配体结合功能中起着不可或缺的作用。
A single amino acid substitution in beta 3 (Asp119 --> Tyr) abrogates the ligand binding function of beta 3 integrins and alters the divalent cation conformation of the platelet integrin alpha IIb beta 3 (GPIIb-IIIa). This aspartic acid residue resides within a conserved cluster of oxygenated residues that may provide ligands for the coordination of divalent cations. To assign function to the other oxygenated residues in this group (Ser121, Ser123, Asp126, Asp127, and Ser130), each of these amino acids in beta 3 was individually substituted by alanine. None of these amino acid substitutions altered heterodimer formation or surface expression. However, the substitutions had differential effects on receptor function. Substitution at positions Asp119 or Ser121 produced a complete loss of receptor function. Cells expressing these mutants failed to adhere to fibrinogen, failed to bind activation-independent ligand-mimetic peptides, and did not bind the ligand-mimetic mAb PAC1 following activation of the receptor. Similarly, cells expressing beta 3 with a substitution at Ser123 also failed to adhere to fibrinogen and did not bind RGD peptide or mAb PAC1. These cells did retain the capacity to bind an alpha IIb beta 3-specific, high affinity peptidomimetic, but occupancy did not induce the conformational change from resting to activated state observed following occupancy of the wild type receptor. Substitution at positions Asp126, Asp127, or Ser130 had no effect on ligand binding function. These data indicate that Asp119, along with Ser121 and Ser123, plays an integral role in the ligand binding function of alpha IIb beta 3.