Human coronaviruses OC43 and HKU1 bind to 9-O-acetylated sialic acids via a conserved receptor-binding site in spike protein domain A
Human coronaviruses OC43 and HKU1 bind to 9-O-acetylated sialic acids via a conserved receptor-binding site in spike protein domain A
复制标题
DOI：
10.1073/pnas.1809667116
复制
发表时间：
2019-02-12
影响因子：
11.1
通讯作者：
de Groot, Raoul J.
中科院分区：
文献类型：
--
作者：
Hulswit, Ruben J. G.;Lang, Yifei;de Groot, Raoul J.
人β冠状病毒OC 43和HKU 1是地方性呼吸道病原体，虽然相关，但起源于独立的人畜共患病引入。OC 43实际上是β冠状病毒1型的宿主范围变体，与牛冠状病毒（BCoV）（其假定的祖先）和猪血凝性脑脊髓炎病毒（PHEV）更密切相关。β 1-冠状病毒（β 1 CoV）和HKU 1使用携带9-O-乙酰化唾液酸（9-O-Ac-Sia）的聚糖受体。受体结合由刺突蛋白S介导，刺突蛋白S是冠状病毒宿主特异性的主要决定因素。对于BCoV，可获得受体结合结构域S1（A）的晶体结构，对于HKU 1，可获得完整S胞外域的冷冻电子显微镜结构。然而，受体结合位点（RBS）的位置，可以说是最重要的信息，是未知的。在这里，我们解决了PHEV S1（A）的3.0埃晶体结构。然后，我们采用比较结构分析方法来绘制β 1 CoV S RBS，使用9-O-Ac-Siabinding位点的一般设计作为蓝图，通过自动配体对接、OC 43、BCoV和PHEV S1（A）的结构指导诱变以及BCoV-S假型水疱性口炎病毒的感染性测定来支持。RBS并非OC 43和相关动物病毒所独有，但显然在HKU 1 S1（A）中也具有保守性和功能性。HKU 1 S RBS对短唾液酸聚糖的结合亲和力显著低于OC 43，我们将其归因于局部结构和可及性的差异，并且这可能指示两种病毒在受体精细特异性方面的差异。我们的研究结果挑战了将OC 43 RBS映射到S1（A）中其他位置以及将HKU 1映射到域S1（B）中的报告。
Human betacoronaviruses OC43 and HKU1 are endemic respiratory pathogens and, while related, originated from independent zoonotic introductions. OC43 is in fact a host-range variant of the species Betacoronavirus-1, and more closely related to bovine coronavirus (BCoV)-its presumptive ancestor-and porcine hemagglutinating encephalomyelitis virus (PHEV). The beta 1-coronaviruses (beta 1CoVs) and HKU1 employ glycan-based receptors carrying 9-O-acetylated sialic acid (9-O-Ac-Sia). Receptor binding is mediated by spike protein S, the main determinant of coronavirus host specificity. For BCoV, a crystal structure for the receptor-binding domain S1(A) is available and for HKU1 a cryoelectron microscopy structure of the complete S ectodomain. However, the location of the receptor-binding site (RBS), arguably the single-most important piece of information, is unknown. Here we solved the 3.0-angstrom crystal structure of PHEV S1(A). We then took a comparative structural analysis approach to map the beta 1CoV S RBS, using the general design of 9-O-Ac-Siabinding sites as blueprint, backed-up by automated ligand docking, structure-guided mutagenesis of OC43, BCoV, and PHEV S1(A), and infectivity assays with BCoV-S-pseudotyped vesicular stomatitis viruses. The RBS is not exclusive to OC43 and related animal viruses, but is apparently conserved and functional also in HKU1 S1(A). The binding affinity of the HKU1 S RBS toward short sialoglycans is significantly lower than that of OC43, which we attribute to differences in local architecture and accessibility, and which may be indicative for differences between the two viruses in receptor fine-specificity. Our findings challenge reports that would map the OC43 RBS elsewhere in S1(A) and that of HKU1 in domain S1(B).