title: Mimivirus giant particles incorporate a large fraction of anonymous and unique gene products.
abstract: Acanthamoeba polyphaga mimivirus is the largest known virus in both particle size and genome complexity. Its 1.2-Mb genome encodes 911 proteins, among which only 298 have predicted functions. The composition of purified isolated virions was analyzed by using a combined electrophoresis/mass spectrometry approach allowing the identification of 114 proteins. Besides the expected major structural components, the viral particle packages 12 proteins unambiguously associated with transcriptional machinery, 3 proteins associated with DNA repair, and 2 topoisomerases. Other main functional categories represented in the virion include oxidative pathways and protein modification. More than half of the identified virion-associated proteins correspond to anonymous genes of unknown function, including 45 "ORFans." As demonstrated by both Western blotting and immunogold staining, some of these "ORFans," which lack any convincing similarity in the sequence databases, are endowed with antigenic properties. Thus, anonymous and unique genes constituting the majority of the mimivirus gene complement encode bona fide proteins that are likely to participate in well-integrated processes.
authors.affiliation: Unité des Rickettsies, CNRS UMR 6020, IFR-48, Faculté de Médecine, 27 Boulevard Jean Moulin, 13385 Marseille, France. patricia.renesto@medecine.univ-mrs.fr
authors.forename: Patricia
authors.initials: P
authors.lastname: Renesto
authors.forename: Chantal
authors.initials: C
authors.lastname: Abergel
authors.forename: Philippe
authors.initials: P
authors.lastname: Decloquement
authors.forename: Danielle
authors.initials: D
authors.lastname: Moinier
authors.forename: Saïd
authors.initials: S
authors.lastname: Azza
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ogata
authors.forename: Patrick
authors.initials: P
authors.lastname: Fourquet
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Gorvel
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Claverie
mesh_terms: D000048:Acanthamoeba / Q000821:virology; D000818:Animals; D004267:DNA Viruses / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D016679:Genome, Viral; D016366:Open Reading Frames; D020543:Proteome; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014764:Viral Proteins / Q000737:chemistry*; D014771:Virion / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D020543:Proteome; D014764:Viral Proteins