Third BIR domain of XIAP binds to both Cu(II) and Cu(I) in multiple sites and with diverse affinities characterized at atomic resolution
Third BIR domain of XIAP binds to both Cu(II) and Cu(I) in multiple sites and with diverse affinities characterized at atomic resolution
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XIAP 的第三个 BIR 结构域在多个位点结合 Cu(II) 和 Cu(I)，并具有原子分辨率下的不同亲和力。
DOI：
10.1038/s41598-019-42875-7
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发表时间：
2019-05-15
影响因子：
4.6
通讯作者：
Su, Xun-Cheng
中科院分区：
文献类型：
--
作者：
Chen, Shen-Na;Fang, Tian;Su, Xun-Cheng
X染色体连锁的凋亡抑制剂XIAP主要是通过其杆状病毒IAP重复（BIR）结构域与半胱天冬酶直接相互作用而被称为半胱天冬酶抑制剂。XIAP具有三个BIR结构域，并且每个BIR结构域含有锌结合位点，通常称为锌指基序。最近的研究表明XIAP参与细胞内铜离子的稳态，BIR结构域结合铜离子。然而，XIAP中第二和第三个BIR结构域BIR2和BIR3与铜的结构细节以及结合模式尚不清楚。在目前的工作中，我们的结构特性的BIR3在溶液中的高分辨率NMR和其他生物物理技术。分析了BIR3与铜在体外和细胞裂解物中的相互作用。我们的研究结果表明，BIR3能够与Cu（II）和Cu（I）形成稳定的复合物，而锌结合位点不受影响，并且在这些相互作用期间锌保持紧密结合在锌指中。令人惊讶的是，BIR3对Cu（II）和Cu（I）具有多个结合位点，但具有不同的结合亲和力。此外，暴露于溶剂的Cys351容易被Cu（II）氧化，导致两个BIR3分子之间的分子间二硫键或细胞裂解物中与谷胱甘肽的混合二硫键。
The X-chromosome linked inhibitor of apoptosis, XIAP, is mainly known as the inhibitor of caspases by direct interaction with caspases with its baculoviral IAP repeat (BIR) domains. XIAP has three BIR domains and each BIR domain contains a zinc binding site, normally known as zinc finger motif. Recent studies showed that XIAP is involved in copper homeostasis in cells and the BIR domains bind copper ion. However, structural details of the second and third BIR domain, BIR2 and BIR3, in XIAP, with copper as well as the binding modes are not known. In the present work we characterize the structural properties of BIR3 in solution by high resolution NMR and other biophysical techniques. The interaction of BIR3 with copper both in vitro and in cell lysates was analyzed. Our results show that BIR3 is able to form stable complexes both with Cu(II) and Cu(I), whereas zinc binding site is not affected and zinc retains tightly bound in the zinc finger during these interactions. Surprisingly, BIR3 has multiple binding sites for Cu(II) and Cu(I) but with varied binding affinities. In addition, the solvent exposed Cys351 is readily oxidized by Cu(II) resulting an intermolecular disulfide bond either between two BIR3 molecules or a mixed disulfide bond with glutathione in cell lysates.