The Research Teams of the Institute of Pathogen Biology Made Significant Progress in the Entry Mechanism of Human Coronavirus HKU1

2017-05-25

On May 23, Nature Communications, a subsidiary journal of Nature, published an article online titled Crystal Structure of the Receptor Binding Domain of The Spike Glycoprotein of Human Betacoronavirus HK-U1. The first authors of this article are Research Assistant Dr. Xiuyuan Ou from the research team of Associate Researcher Chaohui Qian and Dr. Hongxin Guan from the research team of Researcher Sheng Cui of Institute of Pathogen Biology, CAMS. Both Associate Researcher Chaohui Qian and Researcher Sheng Cui of Institute of Pathogen Biology are the corresponding authors.

 

Human coronavirus HKU1 can cause cold in general population. When it comes to infants, the old, and immunocompromised patients, HKU1 infection will induce pneumonia. HKU1 virus, mouse hepatitis virus (MHV), and human coronavirus OC43 are type A coronavirus of βcoronavirus family. It had been found that the S protein receptor binding region of HKU1 virus was located in the C-terminal domain of S1 subunit rather than the traditional N-terminal domain, which was different from MHV and OC43. In this research, by using single-wavelength anomalous diffraction (SAD) technology, the research teams of Chaohui Qian and Sheng Cui analyzed the receptor binding region of HKU1 virus with 1.9 angstroms resolution (see Figure 1), which had three subdomains: core, insertion and subdomain-1 (SD-1). The structures of Core and SD-1 subdomians are highly conservative in different coronaviruses while that of insertion subdomain is highly diversified. Through building the chimera of S protein receptor binding region of different subdomains for HKU1 virus, it was found that the insertion subdomain was the binding position of neutralizing antibody. The further site-directed mutagenesis research found five key amino acids that affected the binding of neutralizing antibody. Finally, two key amino acids affecting the S protein and its binding receptors were found (Figure 2) by conducting a competitive infection experiment in primary airway epithelial cells (Figure 2). In addition, it was found that the interaction between SD-1 and CTD affected the conformational stability of S protein through the mutagenesis of related amino acids on SD-1 of MHV. Therefore, it was believed that the SD-1 might be the crucial node to transmit the conformational variation signal induced by the binding of S protein and receptor to other parts of S protein. This research contributes to a better understanding of entry, immunity and evolution of CoV S proteins.

 

This research is sponsored by CAMS Innovation Fund for Medical Sciences (2016-I2M-1-014), National Natural Science Foundation of China, and National Key Technologies R&D Program.The special thanks go to the team led by Prof. Meitian Wang in SLS Crystallization Platform (X06DA) for providing Native-SAD technology and measuring machine.


 


 

Figure 1      The structure of S Protein receptor binding region of HKU1 virus

 


 


Figure 2      W515 and R517 amino acids: essential for the binding with receptor

 

(Institute of Pathogen Biology)