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Title: Bunyaviridae      
ID:
PRJNA16890
description:
Description of Bunyaviridae adapted from ICTVdb Virion Properties Distinct viral structures are visible in thin sections of infected tissue. Particles contain nucleic acid which is encapsidated. Morphology Virions consist of an envelope and a nucleocapsid. During their life cycle, virions have an extracellular phase; occur in one phenotype only and are encapsidated during extracellular phase. Virus may be sequestered within inclusion bodies that are not occluded and typically contain one nucleocapsid. Virus capsid is enveloped by a single layer envelope. Virions are spherical to pleomorphic. Have no protrusions. Virions measure (80-)100(-120) nm in diameter. The envelope surrounds three nucleocapsids; has surface projections. Surface projections are distinctive spikes covering evenly the surface which are embedded in a lipid bilayer that is 5 nm thick. Surface projections are 5-10 nm long. Host ribosomes are not seen inside the envelope. A regular capsid structure is present. Capsid/nucleocapsid is elongated with helical symmetry. The ribonucleocapsid is filamentous with a length of 200-3000 nm (depending on arrangement) and a width of 2-2.5 nm. The nucleocapsid is not segmented. Nucleocapsids are circular. Virion populations are comprised of particles of uniform size and only one species is recovered in preparations. Physicochemical and Physical Properties The molecular mass (Mr) of virions is 300-400 x 106. Virions have a buoyant density in CsCl of 1.2-1.21 g cm-3; sucrose of 1.16-1.18 g cm-3. The sedimentation coefficient is 350-500 S20w. Virions are sensitive to treatment with detergents, formaldehyde, heat. Nucleic Acid The Mr of the genome constitutes 1-2% of the virion by weight. The genome is monomeric; segmented and consists of three segments of circular; sometimes supercoiled, negative-sense and ambisense, single-stranded RNA that forms a non-covalently closed circle (through hydrogen-bonded ends). Minor species of non-genomic nucleic acid are not found in virions. The complete genome is 10500-22700 nucleotides long. The RNA-L is sequenced, but only an estimate is available, complete sequence is 6300-12000 nucleotides long. RNA-M is sequenced, complete sequence is about 3500-6000 nucleotides long. RNA-S is sequenced and complete sequence is about 1000-2200 nucleotides long. The genome has terminally redundant sequences. The terminally redundant sequences have reiterated terminal sequences. The genome sequence is repeated at both ends. Terminal nucleotides are base-paired, forming non-covalently closed, circular RNAs. Nucleotide sequences at the 3'-terminus are complementary to the 5' end and form a panhandle. The 5'-terminal sequence has conserved regions and repeats complementary to the 3'-terminus; terminal repeats at the 5'-end are 8-11 nucleotides long. The 5'-terminus has no poly (C) tract. The 3'-terminus has conserved nucleotide sequences; of 8-11 nucleotides in length; in each gene segment. The multipartite genome is found in one type of particle only. Each virion contains a single copy of the genome. Proteins Proteins constitute about over 50% of the particle weight. The viral genome encodes structural proteins and non-structural proteins. Lipids Lipids are present and located in the envelope. Virions are composed of 20-30% lipids by weight. The composition of viral lipids is known. The composition of viral lipids and host cell membranes are similar. The lipids are of host origin and are derived from plasma membranes. Viral membranes include phospholipids, sterols, fatty acids, and glycolipids. Lipids are not essential for infectivity. Genome Organization and Replication Coding Strategy of Segment 1: Sequence has no gene blocks. Translation: Replication does not involve a reverse transcription step. Virions are not dependent on a helper virus for replication. Release: The outer envelope acquired by budding. The outer envelope lipids are derived from cellular Golgi membranes, or cell surface membranes (occasionally).
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landingpage: http://www.ncbi.nlm.nih.gov/bioproject/PRJNA16890
authentication:
none
authorization:
none
abbreviation:
NCBI
homePage: http://www.ncbi.nlm.nih.gov
ID:
SCR:006472
name:
National Center for Biotechnology Information
homePage: http://www.ncbi.nlm.nih.gov/bioproject
ID:
SCR:004801
name:
NCBI BioProject