title: Myeloblastosis associated virus (MAV) proteinase site-mutated to be HIV-like has a higher activity and allows production of infectious but morphologically altered virus.
abstract: We have characterized the structure and infectivity of an avian retrovirus, myeloblastosis associated virus (MAV), containing a genetically altered proteinase (PR). A site-directed mutant of MAV-PR that shows an increased proteolytic activity in vitro (about 20 times higher kcat/Km) as a consequence of substituting five amino acids from the substrate-binding pocket with those corresponding to the HIV-1 PR was cloned into a full-sized MAV plasmid. In particular, the wild-type MAV-PR gene was replaced with the mutant one. Despite encoding for an enzyme with increased PR activity, mutant plasmid-transfected turkey fibroblasts displayed an unimpaired virus production in cell cultures. Further, the mutant progeny virus was infectious and its pattern of gag processing products appeared identical to that of wild-type virus. However, by electron microscopy we found that the predominant morphology of mutant viral particles was altered. Instead of a centrally collapsed avian retroviral core, a more diffuse core was visualized for wild-type mutant virions, similar to that observed in mammalian C-type retroviruses.
authors.affiliation: Department of Gene Manipulation, Czechoslovak Academy of Sciences, Prague.
authors.forename: J
authors.initials: J
authors.lastname: Sedlacek
authors.forename: M
authors.initials: M
authors.lastname: Fabry
authors.forename: J E
authors.initials: JE
authors.lastname: Coward
authors.forename: M
authors.initials: M
authors.lastname: Horejsi
authors.forename: P
authors.initials: P
authors.lastname: Strop
authors.forename: R B
authors.initials: RB
authors.lastname: Luftig
mesh_terms: D001355:Alpharetrovirus / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D010450:Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D005347:Fibroblasts / Q000648:ultrastructure; D005814:Genes, Viral; D016333:HIV Protease / Q000378:metabolism; D006378:Helper Viruses / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D007700:Kinetics; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D013379:Substrate Specificity; D014162:Transfection; D014422:Turkeys; D014764:Viral Proteins
chemical_list: D014764:Viral Proteins; D012194:RNA-Directed DNA Polymerase; D010450:Endopeptidases; D016333:HIV Protease