Structure of severe acute respiratory syndrome coronavirus receptor-binding domain complexed with neutralizing antibody.
Structure of severe acute respiratory syndrome coronavirus receptor-binding domain complexed with neutralizing antibody.
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DOI：
10.1074/jbc.m600697200
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发表时间：
2006-06-09
期刊：
影响因子：
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通讯作者：
Dimitrov DS
中科院分区：
文献类型：
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作者：
Prabakaran P;Gan J;Feng Y;Zhu Z;Choudhry V;Xiao X;Ji X;Dimitrov DS
严重急性呼吸综合征冠状病毒（SARS-CoV，或SCV）在2002年和2003年引起了世界范围的流行，通过其包膜（刺突，S）糖蛋白的受体结合结构域（RBD）与受体血管紧张素转换酶2（ACE 2）结合。RBD具有很强的免疫原性;它是一种主要的SCV中和决定簇，可以引发能够竞争ACE 2的强效中和抗体。然而，RBD免疫原性的结构基础、RBD介导的中和作用以及RBD在与ACE 2结合后的进入步骤中的作用尚未阐明。通过使用RBD作为抗原来模拟免疫应答，以筛选来自健康志愿者的大型人抗体库，我们鉴定了一种新的有效的交叉反应性SCV中和单克隆抗体m396，其与ACE 2竞争结合RBD，并确定了RBD-抗体复合物在2.3-δ分辨率下的晶体结构。抗体结合的RBD结构完全确定，揭示了两个先前未解析的片段（残基376-381和503-512）和一个新的二硫键（残基378和511之间）。有趣的是，m396结合的RBD的总体结构与ACE 2结合的RBD的总体结构没有显著不同。抗体表位主要由10个残基长的突出β6-β7环和两个推定的ACE 2结合热点残基（Ile-489和Tyr-491）控制。这些结果为SCV免疫原性和中和作用的主要决定因素的功能、基于抗体互补位和表位的SCV治疗剂的开发以及抗SCV疫苗设计的逆转录疫苗学方法提供了结构上的基本原理。现有的结构信息表明，SCV进入可能不介导的ACE 2诱导的构象变化的RBD，但可能涉及其他构象变化或/和尚未确定的辅助受体。
The severe acute respiratory syndrome coronavirus (SARS-CoV, or SCV), which caused a world-wide epidemic in 2002 and 2003, binds to a receptor, angiotensin-converting enzyme 2 (ACE2), through the receptor-binding domain (RBD) of its envelope (spike, S) glycoprotein. The RBD is very immunogenic; it is a major SCV neutralization determinant and can elicit potent neutralizing antibodies capable of out-competing ACE2. However, the structural basis of RBD immunogenicity, RBD-mediated neutralization, and the role of RBD in entry steps following its binding to ACE2 have not been elucidated. By mimicking immune responses with the use of RBD as an antigen to screen a large human antibody library derived from healthy volunteers, we identified a novel potent cross-reactive SCV-neutralizing monoclonal antibody, m396, which competes with ACE2 for binding to RBD, and determined the crystal structure of the RBD-antibody complex at 2.3-Ä resolution. The antibody-bound RBD structure is completely defined, revealing two previously unresolved segments (residues 376–381 and 503–512) and a new disulfide bond (between residues 378 and 511). Interestingly, the overall structure of the m396-bound RBD is not significantly different from that of the ACE2-bound RBD. The antibody epitope is dominated by a 10-residue-long protruding β6–β7 loop with two putative ACE2-binding hotspot residues (Ile-489 and Tyr-491). These results provide a structural rationale for the function of a major determinant of SCV immunogenicity and neutralization, the development of SCV therapeutics based on the antibody paratope and epitope, and a retrovaccinology approach for the design of anti-SCV vaccines. The available structural information indicates that the SCV entry may not be mediated by ACE2-induced conformational changes in the RBD but may involve other conformational changes or/and yet to be identified coreceptors.