Abstract
Bovine viral diarrhea virus (BVDV) is a member of the genus Pestivirus within the family Flaviviridae. Its single-stranded RNA encodes a polyprotein that is cleaved co- and post-translationally by viral and cellular proteases. However, the cleavage between the envelope proteins Erns and E1 is still unexplained. In this study, an Erns–E1 protein could be identified and characterized with a new E1-specific antiserum. With bicistronic constructs bearing a deletion in the Erns-encoding region and expressing Erns or the Erns–E1 protein, it could be shown that this protein is not essential for virus replication. Furthermore, two putative cleavage sites were mutated in eukaryotic expression plasmids, as well as in full-length cDNA constructs. The mutation of position P3 of a potential signal peptide peptidase site abolished cleavage completely and no infectious virus progeny could be observed, indicating that cleavage of the Erns–E1 protein is indispensable for virus growth.