Amino acid residues in the αIIb subunit that are critical for ligand binding to integrin αIIbβ3 are clustered in the β-propeller model
Amino acid residues in the αIIb subunit that are critical for ligand binding to integrin αIIbβ3 are clustered in the β-propeller model
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DOI：
10.1074/jbc.m107021200
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发表时间：
2001-11-23
影响因子：
4.8
通讯作者：
Takada, Y
中科院分区：
文献类型：
--
作者：
Kamata, T;Tieu, KK;Takada, Y
整合素α 1亚基的几个不同区域与配体结合有关。为了定位α（IIb）中的配体结合位点，我们将所有27个预测环与α（4）或α（5）的相应序列交换。27个交换突变中的19个对与纤维蛋白原和配体模拟抗体（例如LJ-CP 3）的结合没有影响，表明这些区域不含主要配体结合位点。相反，交换剩余的8个预测环完全阻断配体结合。这些关键预测环的Ala扫描诱变鉴定了重复序列2-4中以及重复序列4和5之间的边界处的30多个不连续残基，这些残基对于配体结合至关重要。有趣的是，这些残基聚集在与该模型一致的预测的β-螺旋桨模型中。大多数临界残基位于螺旋桨上表面的边缘，并且几个临界残基位于螺旋桨域的侧面。重复序列1、6和7中的预测环以及β-螺旋桨下表面上的四个推定的Ca 2+结合预测环中没有一个对于配体结合是重要的。结果映射了位于顶部边缘和β-螺旋桨环侧面的重要配体结合界面，以重复序列3为中心。
Several distinct regions of the integrin am, subunit have been implicated in ligand binding. To localize the ligand binding sites in alpha (IIb), we swapped all 27 predicted loops with the corresponding sequences of alpha (4) or alpha (5). 19 of the 27 swapping mutations had no effect on binding to both fibrinogen and ligand-mimetic antibodies (e.g. LJ-CP3), suggesting that these regions do not contain major ligand binding sites. In contrast, swapping the remaining 8 predicted loops completely blocked ligand binding. Ala scanning mutagenesis of these critical predicted loops identified more than 30 discontinuous residues in repeats 2-4 and at the boundary between repeats 4 and 5 as critical for ligand binding. Interestingly, these residues are clustered in the predicted beta -propeller model consistent with this model. Most of the critical residues are located at the edge of the upper face of the propeller, and several critical residues are located on the side of the propeller domain. None of the predicted loops in repeats 1, 6, and 7, and none of the four putative Ca2+ binding predicted loops on the lower surface of the beta -propeller were important for ligand binding. The results map an important ligand binding interface at the edge of the top and on the side of the beta -propeller toroid, centering on repeat 3.