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Title: Cystoviridae      
ID:
PRJNA16866
description:
Description of Cystoviridae adapted from ICTVdb Virion Properties Morphology Phages consist of an envelope, a capsid, and a polymerase complex. Virus capsid is enveloped. Virions are spherical and measure 86 nm in diameter. Surface projections are distinctive spikes covering evenly the surface; comprise P3 adsorption proteins and fusion proteins (P6). Surface projections are composed of one type of protein. Surface projections are 8 nm long. Capsid/nucleocapsid is round and exhibits icosahedral symmetry. The nucleocapsid is isometric and has a diameter of 58 nm. Nucleocapsid contains a polymerase complex; that is dodecahedral in shape; has a diameter of about 43 nm. Physicochemical and Physical Properties The molecular mass (Mr) of virions is 99 x 106, or 40 x 106 (for nucleocapsid). Virions have a buoyant density in CsCl of 1.27 g cm-3; sucrose of 1.24 g cm-3. The sedimentation coefficient is about 405 S20w. Under in vitro conditions virions are stable in acid environment of pH 6; stable in alkaline environment of pH 9. Virions are sensitive to treatment with detergents, ether, and chloroform. Nucleic Acid The Mr of the genome constitutes 10% of the virion by weight. The genome is segmented and consists of three segments of linear, double -stranded RNA. The complete genome is 13379 nucleotides long. RNA-S is fully sequenced, complete sequence is 2948 nucleotides long. The genome has a guanine + cytosine content of 55.2 %, or 56.7 %, or 55.5 % (for L, M and S, respectively). The multipartite genome is found in one type of particle only. Proteins Proteins constitute about about 70% of the particle weight. The viral genome encodes structural proteins and non-structural proteins. Virions consist of 12 structural protein(s) located in the envelope (P9, P10, and P13), peplomers (P3, and P6), nucleocapsid (P8 and P5), polymerase complex (P1, P2, P4, and P7). Structural Proteins: Envelope protein P10 and P13. Envelope protein has a function assigned; is a membrane protein which possess(es) lytic activity (P10, during post-translational processing envelope protein modifications occur that include phosphorylation and myristylation. Envelope protein P3; is involved in absorption; which possess(es) receptor recognition activity; during post-translational processing envelope protein modifications occur that include phosphorylation. Envelope protein P6; is a membrane protein (and serves as anchor for P3, which possess(es) membrane fusion activity. Envelope protein P9; is involved in membrane assembly. Nucleocapsid protein P8; is binding to the genomic RNA. Nucleocapsid protein P5; which possess(es) lytic activity initiating the cell lysis during assembly. Nucleocapsid protein P1, P2, P4 and P7 are early proteins; is polymerase complex. Non-Structural Proteins: One non-structural protein is found. The virus codes for membrane assembly proteins (envelopment of capsid, an RNA-dependent RNA polymerase. 4 internal protein(s) (P1, P2, P4, and P7). Non-structural protein P12. The protein is coded from genome segment S; a membrane assembly protein (needed inside the host cell). Lipids Lipids are present and located in the envelope. Virions are composed of 20% lipids by weight. 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. Carbohydrates Carbohydrates have not been reported. Genome Organization and Replication Phages are adsorbed to specific receptors located on the pili which retract and bring the virion into contact with the host outer membrane, upon contact with the host cell wall virus membrane fuses with the host outer membrane followed by digestion with a lytic enzyme. The process of intracellular uncoating of virions is understood. Virus uncoating occurs in the cell; the viral nucleocapsid is delivered to the cell cytoplasm; the release of the viral polymerase (activates it and the prodution of early transcripts starts). Transcription: Virus transcription is temporally regulated; they are termed early and late. The viral genome is transcribed by virion-associated enzymes. The viral genome is transcribed by a viral polymerase. The translated L transcripts produce the early proteins which assemble to polymerase complexes). Coding Strategy of Segment 1: RNA-L has a unidirectional coding strategy, which is polycistronic, and encodes 4 structural proteins, constituting the polymerase complex. Coding Strategy of Segment 2: RNA-M has a unidirectional coding strategy, has 5 genes that encode 4 structural proteins. The sequence encodes membranes and spikes. Coding Strategy of Segment 3: RNA-S genome is polycistronic, encodes 3 structural proteins for the capsid (coat protein), membrane assembly protein and endopeptidase (lysis and entry) and encodes 1 non-structural protein for envelopment of capsid. Translation: During the replication cycle early synthesis of viral protein is decreased during switch-over to late gene expression. Translation of structural and non-structural proteins occurs in the late stage of replication. Late in infection, the the nucleocapsid surface protein assembles on the polymerase (complex, acts as repressor of the transcription gene). Replication cycle Virions accumulate in the cell cytoplasm. Assembly and Egress: For assembly and packaging a virus specific nonstructural assembly factor is needed to form the nucleocapsid. Viruses assemble in the cytoplasm. Maturation: Virions mature acquiring the membrane from hosts with plasma membranes. Release: Infected cells produce virions. Virus is released from host cell upon death by lysis. The virus envelope is acquired from the host cell during the maturation process in the cytoplasm. Envelope lipids are derived from the host cell plasma membrane.
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landingpage: http://www.ncbi.nlm.nih.gov/bioproject/PRJNA16866
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authorization:
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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