FIG 5.

Structure and function of PdCoV S1-NTD. (A) Structure of PdCoV S1-NTD. The putative sugar-binding site is indicated by the question mark. (B) Structure of α-genus HCoV-NL63 S1-NTD (PDB entry 5SZS). (C) Structure of β-genus BCoV S1-NTD (PDB entry 4H14). (D) ELISA sugar-binding assay for PdCoV S1-NTD. Here, the ELISA plates were precoated with sugar-rich mucin, and then PdCoV S1-NTD was added and incubated with mucin. Mucin-bound S1-NTD was detected using antibodies recognizing its C-terminal His₆ tag. Porcine epidemic diarrhea virus (PEDV) S1 was used as the positive control. PdCoV S1-CTD, SARS-CoV S1-CTD, and BSA were used as negative controls. A plate without mucin was used as an additional negative control. Statistical analyses were performed using two-tailed t test. Error bars indicate standard errors of the means (SEM) (n = 5). ***, P < 0.001.