FIG 1 .

Expression and characterization of SGRPs. (A) Cartoon schematic of SGRPs. Nidovirus HE ectodomains were expressed with a C-terminal tag of the human IgG Fc domain and a 6-His sequence. The esterase active site Ser (denoted by red squares) was mutated to Ala to generate binding SGRPs. (B) Expressed and purified SGRPs resolved on SDS-PAGE. (C) MHV-S HE-Fc treated with various glycosidases and resolved on SDS-PAGE shows presence of N-linked (but not O-linked) glycosylation. (D) Solid-phase lectin binding assays of SGRPs. Plates were coated with horse serum (MHV-S) or bovine submaxillary mucin (PToV-P4, BCoV-Mebus) and probed with 2-fold dilutions of SGRPs (starting at 50 μg/ml). Parallel rows were treated during blocking with active-esterase forms of the proteins (Est+).