Crystal structure of histidine-rich glycoprotein N2 domain reveals redox activity at an interdomain disulfide bridge: implications for angiogenic regulation
Crystal structure of histidine-rich glycoprotein N2 domain reveals redox activity at an interdomain disulfide bridge: implications for angiogenic regulation
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DOI：
10.1182/blood-2013-11-535963
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发表时间：
2014-03-20
期刊：
影响因子：
20.3
通讯作者：
Stewart, Alan J.
中科院分区：
文献类型：
--
作者：
Kassaar, Omar;McMahon, Stephen A.;Stewart, Alan J.
富组氨酸糖蛋白（HRG）是一种由6个不同功能域组成的血浆蛋白，是血管生成和凝血等关键心血管过程的重要调节因子。该蛋白由2个n端结构域（N1和N2）、2个富含脯氨酸的区域（PRR1和PRR2）组成，它们位于一个富含组氨酸的区域（HRR）的侧面，以及一个c端结构域。迄今为止，HRG的结构信息主要来自序列分析和光谱研究。据认为，含有HRR的HRG片段通过纤溶酶介导的裂解释放，在体内作为血管生成的负调节因子。然而，它的释放也需要裂解二硫键，这表明它的活性是由氧化还原过程介导的。在这里，我们展示了血清纯化兔HRG的N2结构域的1.93埃分辨率晶体结构。该结构证实了N2结构域与N1结构域一起在HRG上形成一个重要的分子相互作用位点，具有一个类似胱抑素的折叠，该折叠由缠绕在5转α -螺旋上的5股反平行β片组成。在Asn184上发现了一个天然的n链糖基化位点。此外，该结构揭示了Cys185上存在s -谷胱甘肽加合物，这可能与HRG抗血管生成裂解产物的氧化还原介导释放有关。
Histidine-rich glycoprotein (HRG) is a plasma protein consisting of 6 distinct functional domains and is an important regulator of key cardiovascular processes, including angiogenesis and coagulation. The protein is composed of 2 N-terminal domains (N1 and N2), 2 proline-rich regions (PRR1 and PRR2) that flank a histidine-rich region (HRR), and a C-terminal domain. To date, structural information of HRG has largely come from sequence analysis and spectroscopic studies. It is thought that an HRG fragment containing the HRR, released via plasmin-mediated cleavage, acts as a negative regulator of angiogenesis in vivo. However, its release also requires cleavage of a disulphide bond suggesting that its activity is mediated by a redox process. Here, we present a 1.93 angstrom resolution crystal structure of the N2 domain of serum-purified rabbit HRG. The structure confirms that the N2 domain, which along with the N1 domain, forms an important molecular interaction site on HRG, possesses a cystatin-like fold composed of a 5-stranded antiparallel beta-sheet wrapped around a 5-turn alpha-helix. A native N-linked glycosylation site was identified at Asn184. Moreover, the structure reveals the presence of an S-glutathionyl adduct at Cys185, which has implications for the redox-mediated release of the antiangiogenic cleavage product from HRG.