Leader cysteine autoprotease that cleaves itself from the nascent polyprotein during translation of the viral mRNA. Once released, plays a role in the inhibition of host innate immune response by interacting with host IRF3 and inducing its proteasomal degradation. Packages viral RNA to form a viral nucleocapsid and thereby protects viral RNA. Also plays a role in transcription regulation. Protects the incoming virus against IFN-induced effectors. Initial binding to target cell probably involves interaction of E(rns) with glycosaminoglycans. E1 and/or E2 are probably responsible of cell attachment with CD46 and subsequent fusion after internalization of the virion by endocytosis. E1 and/or E2 are probably responsible of cell attachment with CD46 and subsequent fusion after internalization of the virion by endocytosis. Plays an essential role in the virus replication cycle by acting as a viroporin (By similarity). Forms ion conductive pores, which alters the cell permeability allowing the transport of ions and other small molecules (By similarity). Forms a leader sequence to properly orient NS2 in the membrane. Uncleaved NS2-3 is required for production of infectious virus. Plays a role in the regulation of viral RNA replication. Multifunctional protein that contains an N-terminal protease and a C-terminal helicase, playing essential roles in viral polyprotein processing and viral genome replication. The chymotrypsin-like serine protease activity utilizes NS4A as an essential cofactor and catalyzes the cleavage of the polyprotein leading to the release of NS4A, NS4B, NS5A, and NS5B. Interacts with NS5B to enhance RNA-dependent RNA polymerase activity. Acts as a cofactor for the NS3 protease activity. Induces a specific membrane alteration that serves as a scaffold for the virus replication complex. Replicates the viral (+) and (-) genome. Leu is conserved at position P1 for all four cleavage sites. Alanine is found at position P1' of the NS4A-NS4B cleavage site, whereas serine is found at position P1' of the NS3-NS4A, NS4B-NS5A and NS5A-NS5B cleavage sites. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) a ribonucleoside 5'-triphosphate + H2O = a ribonucleoside 5'-diphosphate + H(+) + phosphate ATP + H2O = ADP + H(+) + phosphate Homodimer; disulfide-linked. Homodimer; disulfide-linked (By similarity). Heterodimer with E1; disulfide-linked (By similarity). Homodimer; disulfide-linked (By similarity). Heterodimer with E1; disulfide-linked (By similarity). The C-terminus membrane anchor of Erns represents an amphipathic helix embedded in plane into the membrane. Heavily glycosylated. The viral RNA of pestiviruses is expressed as a single polyprotein which undergoes post-translational proteolytic processing resulting in the production of at least eleven individual proteins. The N-terminal protease cleaves itself from the nascent polyprotein autocatalytically and thereby generates the N-terminus of the adjacent viral capsid protein C. Cleavage between E2 and p7 is partial. BVDV is divided in two types: cytopathic and non-cytopathic. Both types of viruses can be found in animals suffering from mucosal disease, as a cytopathic BVDV can develop from a non-cytopathic virus within the infected animal by deletions, mutations or insertions. Both types express uncleaved NS2-3, but cytopathic strains also express NS3. Belongs to the pestivirus polyprotein family.