title: Structural studies of the Sputnik virophage.
abstract: The virophage Sputnik is a satellite virus of the giant mimivirus and is the only satellite virus reported to date whose propagation adversely affects its host virus' production. Genome sequence analysis showed that Sputnik has genes related to viruses infecting all three domains of life. Here, we report structural studies of Sputnik, which show that it is about 740 A in diameter, has a T=27 icosahedral capsid, and has a lipid membrane inside the protein shell. Structural analyses suggest that the major capsid protein of Sputnik is likely to have a double jelly-roll fold, although sequence alignments do not show any detectable similarity with other viral double jelly-roll capsid proteins. Hence, the origin of Sputnik's capsid might have been derived from other viruses prior to its association with mimivirus.
authors.affiliation: Department of Biological Sciences, Purdue University, 915 W. State Street, West Lafayette, IN 47907-2054, USA.
authors.forename: Siyang
authors.initials: S
authors.lastname: Sun
authors.forename: Bernard
authors.initials: B
authors.lastname: La Scola
authors.forename: Valorie D
authors.initials: VD
authors.lastname: Bowman
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Ryan
authors.forename: Julian P
authors.initials: JP
authors.lastname: Whitelegge
authors.forename: Didier
authors.initials: D
authors.lastname: Raoult
authors.forename: Michael G
authors.initials: MG
authors.lastname: Rossmann
mesh_terms: D000048:Acanthamoeba / Q000821:virology*; D000818:Animals; D002213:Capsid / Q000737:chemistry; D020285:Cryoelectron Microscopy; D003460:Crystallization; D021621:Imaging, Three-Dimensional; D013058:Mass Spectrometry; D056686:Mimiviridae / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure*; D012526:Satellite Viruses / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure*; D014771:Virion / Q000737:chemistry / Q000648:ultrastructure