title: Processing of GB virus B non-structural proteins in cultured cells requires both NS3 protease and NS4A cofactor.
abstract: The identification of antivirals and vaccines against hepatitis C virus (HCV) infection is hampered by the lack of convenient animal models. The need to develop surrogate models has recently drawn attention to GB virus B (GBV-B), which produces hepatitis in small primates. In a previous study in vitro, it was shown that GBV-B NS3 protease shares substrate specificity with the HCV enzyme, known to be crucial for virus replication. In this report, GBV-B NS3 activity on GBV-B precursor proteins has been analysed in a cell-based system. It is shown that mature protein products are obtained that are compatible with the cleavage sites proposed on the basis of sequence homology with HCV and that GBV-B NS4A protein is required as a cofactor for optimal enzymatic activity. Experiments in vitro supported by a structural model mapped the region of NS4A that interacts with NS3 and showed that the GBV-B cofactor cannot be substituted for by its HCV analogue.
authors.affiliation: Istituto di Ricerche di Biologia Molecolare P. Angeletti (IRBM), Via Pontina Km 30.600, 00040 Pomezia (Roma), Italy1.
authors.forename: Andrea
authors.initials: A
authors.lastname: Sbardellati
authors.affiliation: Istituto di Ricerche di Biologia Molecolare P. Angeletti (IRBM), Via Pontina Km 30.600, 00040 Pomezia (Roma), Italy1.
authors.forename: Elisa
authors.initials: E
authors.lastname: Scarselli
authors.affiliation: Istituto di Ricerche di Biologia Molecolare P. Angeletti (IRBM), Via Pontina Km 30.600, 00040 Pomezia (Roma), Italy1.
authors.forename: Viviana
authors.initials: V
authors.lastname: Amati
authors.affiliation: Istituto di Ricerche di Biologia Molecolare P. Angeletti (IRBM), Via Pontina Km 30.600, 00040 Pomezia (Roma), Italy1.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Falcinelli
authors.affiliation: Institut für Medizinische Mikrobiologie, Martin-Luther-Universität Halle-Wittenberg, Magdeburger Str. 6, D-06097 Halle (Saale), Germany2.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Kekulé
authors.affiliation: Istituto di Ricerche di Biologia Molecolare P. Angeletti (IRBM), Via Pontina Km 30.600, 00040 Pomezia (Roma), Italy1.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Traboni
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000956:Antigens, Viral / Q000378:metabolism*; D002427:Cebidae; D002478:Cells, Cultured; D018067:Flaviviridae / Q000502:physiology*; D016174:Hepacivirus / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals; D020365:RNA Helicases / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D014779:Virus Replication; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D000956:Antigens, Viral; D021382:Protein Sorting Signals; D020365:RNA Helicases; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; C060028:NS3 protein, flavivirus; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C080106:NS4A protein, flavivirus