title: Conserved determinants for membrane association of nonstructural protein 5A from hepatitis C virus and related viruses.
abstract: Nonstructural protein 5A (NS5A) is a membrane-associated essential component of the hepatitis C virus (HCV) replication complex. An N-terminal amphipathic alpha helix mediates in-plane membrane association of HCV NS5A and at the same time is likely involved in specific protein-protein interactions required for the assembly of a functional replication complex. The aim of this study was to identify the determinants for membrane association of NS5A from the related GB viruses and pestiviruses. Although primary amino acid sequences differed considerably, putative membrane anchor domains with amphipathic features were predicted in the N-terminal domains of NS5A proteins from these viruses. Confocal laser scanning microscopy, as well as membrane flotation analyses, demonstrated that NS5As from GB virus B (GBV-B), GBV-C, and bovine viral diarrhea virus, the prototype pestivirus, display membrane association characteristics very similar to those of HCV NS5A. The N-terminal 27 to 33 amino acid residues of these NS5A proteins were sufficient for membrane association. Circular dichroism analyses confirmed the capacity of these segments to fold into alpha helices upon association with lipid-like molecules. Despite structural conservation, only very limited exchanges with sequences from related viruses were tolerated in the context of functional HCV RNA replication, suggesting virus-specific interactions of these segments. In conclusion, membrane association of NS5A by an N-terminal amphipathic alpha helix is a feature shared by HCV and related members of the family Flaviviridae. This observation points to conserved roles of the N-terminal amphipathic alpha helices of NS5A in replication complex formation.
authors.affiliation: Department of Medicine II, University of Freiburg, D-79106 Freiburg, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Brass
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Pal
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sapay
authors.forename: Gilbert
authors.initials: G
authors.lastname: Deléage
authors.forename: Hubert E
authors.initials: HE
authors.lastname: Blum
authors.forename: François
authors.initials: F
authors.lastname: Penin
authors.forename: Darius
authors.initials: D
authors.lastname: Moradpour
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D002417:Cattle; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D002942:Circular Dichroism; D017124:Conserved Sequence; D001908:Diarrhea Viruses, Bovine Viral / Q000737:chemistry*; D018274:Electroporation; D029405:GB virus A / Q000737:chemistry*; D029406:GB virus B / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D012516:Osteosarcoma / Q000473:pathology; D010455:Peptides / Q000737:chemistry; D014176:Protein Biosynthesis; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013752:Tetracycline / Q000494:pharmacology; D014162:Transfection; D017361:Viral Nonstructural Proteins / Q000737:chemistry*; D012324:RNA-Dependent RNA Polymerase
chemical_list: D000596:Amino Acids; D010455:Peptides; D013752:Tetracycline; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase