The Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China.
Comprehensive AIDS Research Center, Beijing Advanced Innovation Center for Structural Biology, School of Medicine and Vanke School of Public Health, Tsinghua University, Beijing, China.
Structure. 2022 Oct 6;30(10):1432-1442.e4. doi: 10.1016/j.str.2022.07.005. Epub 2022 Aug 1.
Severe acute respiratory syndrome coronavirus (SARS-CoV), SARS-CoV-2, and human coronavirus (hCoV)-NL63 utilize ACE2 as the functional receptor for cell entry, which leads to zoonotic infection. Horses (Equus caballus) attracted our attention because the spike protein receptor-binding domains (RBDs) of SARS-CoV-2 and SARS-CoV-2-related coronaviruses bind equine ACE2 (eACE2) with high affinity. Here we show that eACE2 binds the RBDs of these three coronaviruses and also SARS-CoV-2 variants but with lower affinities compared with human ACE2 (hACE2). Structural analysis and mutation assays indicated that eACE2-H41 accounts for the lower binding affinity of eACE2 to the RBDs of SARS-CoV-2 variants (Alpha, Beta, and Gamma), SARS-CoV, and hCoV-NL63. Pseudovirus infection assays showed that the SARS-CoV-2 Delta strain (B.1.617.2) displayed a significantly increased infection efficiency in eACE2-expressing HeLa cells. Our results reveal the molecular basis of eACE2 binding to the RBDs of SARS-CoV, SARS-CoV-2, and hCoV-NL63, which provides insights into the potential animal transmission of these ACE2-dependent coronaviruses.
严重急性呼吸综合征冠状病毒（SARS-CoV）、SARS-CoV-2 和人类冠状病毒（hCoV）-NL63 均利用 ACE2 作为细胞进入的功能性受体，从而导致人畜共患感染。马（Equus caballus）引起了我们的注意，因为 SARS-CoV-2 和 SARS-CoV-2 相关冠状病毒的刺突蛋白受体结合域（RBD）与马 ACE2（eACE2）具有高亲和力。在这里，我们表明 eACE2 结合了这三种冠状病毒以及 SARS-CoV-2 变体的 RBD，但与 hACE2（人 ACE2）相比亲和力较低。结构分析和突变实验表明，eACE2-H41 导致 eACE2 与 SARS-CoV-2 变体（Alpha、Beta 和 Gamma）、SARS-CoV 和 hCoV-NL63 的 RBD 的结合亲和力较低。假病毒感染实验表明，SARS-CoV-2 Delta 株（B.1.617.2）在表达 eACE2 的 HeLa 细胞中显示出显著提高的感染效率。我们的结果揭示了 eACE2 与 SARS-CoV、SARS-CoV-2 和 hCoV-NL63 的 RBD 结合的分子基础，为这些依赖 ACE2 的冠状病毒在动物中的潜在传播提供了线索。
