Scaling was performed with XSCALE. subdomain-1 (SD-1). While the structure of the core and SD-1 subdomains of HKU1 are highly much like those of other -CoVs, the insertion subdomain adopts a novel fold, which is largely invisible in the cryo-EM structure of the HKU1 S trimer. We identify five residues in the insertion subdomain that are critical for binding of neutralizing antibodies and two residues essential for receptor binding. Our study contributes to a better understanding of access, immunity and development of CoV S proteins. Coronaviruses (CoV) are enveloped, plus-stranded RNA viruses with a genome of 30?Kb, the largest among all known RNA viruses1. Phylogenetically, they are divided into four genera: -CoV, -CoV, -CoV and -CoV (ref. 2). Rabbit polyclonal to HSD17B12 Since 2002, there have been two pandemics of fatal pneumonia caused by CoVs. Severe acute respiratory syndrome coronavirus (SARS-CoV) emerged in China in 2002 (refs 3, 4, 5), and the Middle East respiratory syndrome coronavirus (MERS-CoV) emerged in 2012 and remains endemic in the Middle East6. In addition to SARS-CoV and MERS-CoV, four additional Geniposide endemic human CoVs, 229E, NL63, OC43 and HKU1, are actively circulating in the human population and their contamination accounts for 15C30% of acute respiratory illnesses7. While 229E and NL63 are -CoVs, OC43 and HKU1 are -CoVs. The human HKU1 coronavirus is usually a lineage A -CoV and is comprised of Geniposide three genotypes (A, B and C)8. The virus was first discovered in Hong Kong in 2004 during post-SARS pandemic surveillance9. An HKU1 contamination generally results in moderate upper respiratory tract disease, but can occasionally cause severe respiratory diseases including pneumonia in very young children, the elderly, and immunocompromised patients10. HKU1 can only be propagated in well-differentiated main human tracheal bronchial epithelial (HTBE) cells and human alveolar type II (hATII) cells11,12,13,14. Although contamination of multiple cell lines including A549 cells by HKU1 S protein pseudotyped lentiviruses has been reported15, efforts to repeat these results were unsuccessful14,16. The binding of (?)86.72, 183.99, 63.1686.56, 183.80, 63.34??()90.00, 90.00, 90.0090.00, 90.00, 90.00?X-ray sourceSLS BEAMLINE X06DASLS BEAMLINE X06DA?Wavelength (?)2.08 (for sulfur phasing)1.00 (native data set)?Data range (?)49.20C2.3049.26C1.91?Reflections unique43,316*75,702*?factor for 5% of reflections against Geniposide which the model was not refined. ||100th percentile is the best among structures of comparable resolution; 0th percentile is the worst. For clashscore the comparative set of structures was selected in 2004, for MolProbity score in 2006. Structure of HKU1 CTD In this structure, we located 364 out of 368 amino acids of 1A-S310-677aa in the electron density and found that four residues, N355, N433, N454 and N470, were glycosylated (Fig. 4b). The structure consists of three subdomains: the core, the insertion or variable loop, and the SD-1.The core and insertion loop form the CTD of the HKU1 S1 subunit. The overall structure of 1A-S310-677aa resembles the shape of a two-arm boomerang with the core and SD-1 subdomains in one arm and the insertion loop in the other arm. The core subdomain of 1A-S310-677aa is usually comprised of residues from 311 to 428 and 589 to 613, and has nine -linens (1-7, 13-14) and five helices (1-5) (Fig. 2). The topology of the core Geniposide subdomain is usually highly much like those of SARS-CoV, MERS-CoV, HKU4 and MHV (Fig. 3). Five-stranded anti-parallel -linens (3-7, 13) are sandwiched by five connecting helices (1-5) with 1, 2 and 3 on one side and 4 and 5 on the other side (Fig. 2). The structure is further stabilized by three pairs of disulfide bonds between cysteine 327 and 352, 370 and 423, and 382 and 605 (Fig. 2a and Supplementary Fig. 1). These disulfide bridges are also conserved in the CTDs of SARS-CoV and MERS-CoV. Open in a separate window Physique 4 Integrated model of HKU1 S protein trimer with the crystal structure of 1A-S310-677aa.(a) The trimeric model of HKU1 S protein with the crystal structure of 1A-S310-677aa. (left) side view; (right) top view. The model is built by superimposing the crystal structure of 1A-S310-677aa into the Cryo-EM structure of the HKU1 S protein trimer18 based on the structure alignment of the core subdomain. The.
Scaling was performed with XSCALE