A unique bivalent binding and inhibition mechanism by the yatapoxvirus interleukin 18 binding protein.
A unique bivalent binding and inhibition mechanism by the yatapoxvirus interleukin 18 binding protein.
复制标题
DOI：
10.1371/journal.ppat.1002876
复制
发表时间：
2012
期刊：
影响因子：
6.7
通讯作者：
Deng J
中科院分区：
文献类型：
--
作者：
Krumm B;Meng X;Wang Z;Xiang Y;Deng J
白介素18(IL18)是一种细胞因子，在炎症和宿主对微生物的防御中发挥重要作用。哺乳动物编码一种被称为IL18结合蛋白(IL18BP)的IL18可溶性抑制物，它通过负反馈机制调节IL18的活性。许多痘病毒编码同源的IL18BP，这有助于毒力。以往对IL18和IL18BPs的结构和功能研究表明，IL18上有一个重要的结合热点，涉及IL18上的一个赖氨酸和IL18BPs上的两个芳香族残基。在非常多样化的哺乳动物和痘病毒IL18BPs中，芳香族残基是保守的，但YatapoxVirus IL18BPs除外，它缺乏关键的苯丙氨酸残基。为了了解YATAPOX病毒IL18BPs中和IL18的机制，我们以1.75？分辨率解算了YLDV IL18BP和IL18复合体的晶体结构。YLDV-IL18BP以2：2的化学计量比与IL18形成二硫键结合的同源二聚体，而不是ECV(ECTV)IL18BP和IL18的1：1复合体。二聚体界面的破坏导致了功能单体的产生，但结合亲和力降低了3倍。YLDV-IL18BP：IL18复合体的总体结构类似于ECTV-IL18BP：IL18复合体，尽管缺乏关键的赖氨酸-苯丙氨酸相互作用。通过结构和诱变研究，确定了YLDV-IL18BP：IL18结合界面特有的接触残基，包括YLDV-IL18BP的Q67、P116和IL18的Y1、S105和D110。总之，我们的研究表明，YLDV-IL18BP在哺乳动物和痘病毒IL-18BP的不同家族中是独一无二的，因为它使用二价结合模式和一组独特的相互作用残基来结合IL18。然而，尽管存在着广泛的分歧，YLDV-IL18BP与其他IL18BP所用的IL18相同的表面结合，表明所有IL18BP都通过阻断IL18上假定的受体结合位点而使用一种保守的抑制机制。白介素18(IL18)是一种重要的炎症和免疫细胞因子。哺乳动物和痘病毒编码IL18的同源抑制蛋白，称为IL18BPs，调节IL18的活性，并在病毒蛋白的情况下，有助于毒力。以往的结构和功能研究表明，IL18：IL18BP界面上的残基对高亲和力结合至关重要，包括IL18BPs上的苯丙氨酸，它在几乎所有IL18BPs中都是保守的，但YatapoxVirus IL18BPs除外。为了了解YATAPOX病毒IL18BP中和IL18的机制，我们解算了YLDV IL18BP：IL18复合体的高分辨晶体结构。该结构显示了2：2的二价结合络合物，这在任何其他IL18BPs中都没有观察到。通过突变和功能研究，我们发现了一组YLDV-IL18BP和IL18结合所特有的相互作用残基，可能弥补了保守的苯丙氨酸相互作用的缺失。然而，尽管存在这种广泛的分歧，YLDV-IL18BP与其他IL18BP使用的IL18表面结合。我们的研究表明，所有IL18BP都通过阻断IL18上假定的受体结合位点而使用保守的抑制机制，但IL18上的界面可被广泛而多样的哺乳动物和痘病毒IL18BP家族延展。
Interleukin 18 (IL18) is a cytokine that plays an important role in inflammation as well as host defense against microbes. Mammals encode a soluble inhibitor of IL18 termed IL18 binding protein (IL18BP) that modulates IL18 activity through a negative feedback mechanism. Many poxviruses encode homologous IL18BPs, which contribute to virulence. Previous structural and functional studies on IL18 and IL18BPs revealed an essential binding hot spot involving a lysine on IL18 and two aromatic residues on IL18BPs. The aromatic residues are conserved among the very diverse mammalian and poxviruses IL18BPs with the notable exception of yatapoxvirus IL18BPs, which lack a critical phenylalanine residue. To understand the mechanism by which yatapoxvirus IL18BPs neutralize IL18, we solved the crystal structure of the Yaba-Like Disease Virus (YLDV) IL18BP and IL18 complex at 1.75 Å resolution. YLDV-IL18BP forms a disulfide bonded homo-dimer engaging IL18 in a 2∶2 stoichiometry, in contrast to the 1∶1 complex of ectromelia virus (ECTV) IL18BP and IL18. Disruption of the dimer interface resulted in a functional monomer, however with a 3-fold decrease in binding affinity. The overall architecture of the YLDV-IL18BP:IL18 complex is similar to that observed in the ECTV-IL18BP:IL18 complex, despite lacking the critical lysine-phenylalanine interaction. Through structural and mutagenesis studies, contact residues that are unique to the YLDV-IL18BP:IL18 binding interface were identified, including Q67, P116 of YLDV-IL18BP and Y1, S105 and D110 of IL18. Overall, our studies show that YLDV-IL18BP is unique among the diverse family of mammalian and poxvirus IL-18BPs in that it uses a bivalent binding mode and a unique set of interacting residues for binding IL18. However, despite this extensive divergence, YLDV-IL18BP binds to the same surface of IL18 used by other IL18BPs, suggesting that all IL18BPs use a conserved inhibitory mechanism by blocking a putative receptor-binding site on IL18. Interleukin 18 (IL18) is an important cytokine in inflammation and immunity. Mammals and poxviruses encode homologous inhibitory proteins of IL18, named IL18BPs, which regulate IL18 activity and, in the case of the viral proteins, contribute to virulence. Previous structural and functional studies revealed residues at IL18:IL18BP interface that are critical for the high-affinity binding, including a phenylalanine on IL18BPs, which is conserved among nearly all IL18BPs with the notable exception of yatapoxvirus IL18BPs. To understand the mechanism by which yatapoxvirus IL18BPs neutralize IL18, we solved the high-resolution crystal structure of the Yaba-Like Disease Virus (YLDV) IL18BP:IL18 complex. The structure revealed a 2∶2 bivalent binding complex, which has not been observed in any other IL18BPs. Through mutagenesis and functional studies, we found a set of interacting residues that are unique for the association of YLDV-IL18BP and IL18, likely compensating for the lack of the interactions involving the conserved phenylalanine. Despite this extensive divergence, however, YLDV-IL18BP binds to the same surface of IL18 used by other IL18BPs. Our study suggests that all IL18BPs use a conserved inhibitory mechanism by blocking a putative receptor-binding site on IL18 but the interface on IL18 is malleable by a broad and diverse family of mammalian and poxvirus IL18BPs.
登录
查看更多内容
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
5.8
作者：
Larkin, M. A.;Blackshields, G.;Higgins, D. G.
通讯作者：
Higgins, D. G.
影响因子：
2.2
作者：
Huang, Bao-Cheng;Davern, Sandra;Kennel, Stephen J.
通讯作者：
Kennel, Stephen J.
DOI：
10.1107/s0907444902016657
发表时间：
2002-11-01
影响因子：
2.2
作者：
Adams, PD;Grosse-Kunstleve, RW;Terwilliger, TC
通讯作者：
Terwilliger, TC
影响因子：
5.5
作者：
Dinarello, CA
通讯作者：
Dinarello, CA