Minor envelope protein. Part of the glycoproteins heterotrimer GP2b-GP3-GP4 which is probably responsible for the attachment to target host cell. This attachment induces virion internalization predominantly through clathrin-dependent endocytosis. Heterotrimer of GP2b, GP3, and GP4; disulfide-linked (Probable). The GP2b-GP3-GP4 complex associates with the E protein (By similarity). Only a small fraction of GP3 synthesized in infected cells ends up in virions. The signal sequence functions as an uncleaved signal when glycosylated at Asn-28 and Asn-29. When the protein is not glycosylated at these sites, the signal sequence is cleaved (PubMed:24142700). N-glycosylation for overlapping sequons occurs at both Asn-28 and Asn-29, and blocks cleavage of the signal peptide between Gly-26 and Ser-27. Belongs to the arteriviridae GP3 protein family.