title: Protein P4 of double-stranded RNA bacteriophage phi 6 is accessible on the nucleocapsid surface: epitope mapping and orientation of the protein.
abstract: Protein P4, an early protein of double-stranded RNA bacteriophage phi 6, is a component of the virion-associated RNA polymerase complex and possesses a nucleoside triphosphate (NTP) phosphohydrolase activity. We have produced and characterized a panel of 20 P4-specific monoclonal antibodies. Epitope mapping using truncated molecules of recombinant P4 revealed seven linear epitopes. The accessibility of the epitopes on the phi 6 nucleocapsid (NC) surface showed that at least the C terminus and an internal domain, containing the consensus sequence for NTP binding, protrude the NC shell. Four of the NC-binding antibodies distorted the integrity of the NC by releasing protein P4 and the major NC surface protein P8. This finding suggests a close contact between these two proteins. The dissociation of the NC led to the activation of the virion-associated RNA polymerase. The multimeric status of the recombinant P4 was similar to that of the virion-associated P4, indicating that no accessory virus proteins are needed for its multimerization.
authors.affiliation: Department of Genetics, University of Helsinki, Finland.
authors.forename: P M
authors.initials: PM
authors.lastname: Ojala
authors.forename: J T
authors.initials: JT
authors.lastname: Juuti
authors.forename: D H
authors.initials: DH
authors.lastname: Bamford
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D001483:Base Sequence; D002213:Capsid / Q000276:immunology*; D003001:Cloning, Molecular; D012321:DNA-Directed RNA Polymerases / Q000276:immunology* / Q000378:metabolism; D000939:Epitopes / Q000276:immunology*; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011487:Protein Conformation; D017105:Pseudomonas Phages / Q000201:enzymology*; D012317:RNA Phages / Q000201:enzymology* / Q000276:immunology / Q000302:isolation & purification; D012330:RNA, Double-Stranded; D017384:Sequence Deletion; D014764:Viral Proteins / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D012330:RNA, Double-Stranded; D014764:Viral Proteins; C080701:protein P4 (Pseudomonas); D012321:DNA-Directed RNA Polymerases; D010744:Phosphoric Monoester Hydrolases