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Title: Paramyxoviridae      
ID:
PRJNA16882
description:
Description of Paramyxoviridae adapted from ICTVdb Virion Properties Morphology Virions consist of an envelope, a nucleocapsid, and a matrix protein. During their life cycle, virions have an extracellular phase. Virus capsid is enveloped and mature naturally by budding through the membrane of the host cell; spherical to pleomorphic; filamentous and other forms are common. Virions measure (60-)150-200 nm in diameter; 1000-10000 nm in length. The envelope has surface projections. Surface projections are spaced widely apart, distinctive spikes of haemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins covering evenly the surface; embedded in a lipid bilayer which is comprises hemagglutinin and neuraminidase (HN), or hemagglutinin (H), or surface glycoproteins (GP), or fusion proteins. Surface projections are homo-oligomers and form spike-like projections of 8-12 nm long; spaced 6-10 nm apart (depending on the genus). Capsid/nucleocapsid is elongated and exhibits helical symmetry. The nucleocapsid is filamentous, flexuous with a varying length with a length of 600-800(-1000) nm (depending on the genus) and a width of 13-18 nm. Basic helix is obvious. Pitch of helix is 5.5-7 nm (depending on the subfamily). The nucleocapsid is not segmented. Physicochemical and Physical Properties The molecular mass (Mr) of virions is 500 x 106 (occassionally, multiploid virions are found with a greater Mr). Virions have a buoyant density in CsCl of 1.18-1.31 g cm-3; sucrose of 1.18-1.2 g cm-3. The sedimentation coefficient is at least 1000 S20w. Virions are sensitive to treatment with lipid solvents, non-ionic detergents, formaldehyde, oxidizing agents, heat (to the extreme). Nucleic Acid The Mr of the genome constitutes 0.5% of the virion by weight (; the Mr of the genome is 5-7 x 106). The genome is usually monomeric, or multiploid (sometimes, not segmented and contains a single molecule of linear negative-sense, single-stranded RNA. The genome is not infectious (by itself). Virions may also contain occasionally a positive sense single-stranded copy of the genome (thus, partial self-annealing of extracted RNA may occur). The complete genome is 15200-15900 nucleotides long. The RNA is sequenced and complete sequence is about 15200-15900 nucleotides long and encodes 7-9/9-11, namely three nucleocapsid-associated proteins (N or NP; P and L, three membrane-associated proteins, a matrix protein M and two envelope proteins (F and G, or H, or HN). The 5'-end of the negative-sense strand does not have a covalently attached terminal protein; genome does not have cap. The 3'-terminus has no poly (A) tract. Each virion contains a single copy of the genome; a full length copy (of RNA exclusively as nucleocapsid, or intracellularly). Proteins Proteins constitute about about 75-80% of the particle weight. The viral genome encodes structural proteins and non-structural proteins. Virions consist of 6-7 structural protein(s) located in the nucleocapsid, envelope, membrane, and matrix. The viral envelope contains 2 integral membrane proteins. Structural Proteins: Envelope protein F. Envelope protein has a function assigned; is a fusion protein. During post-translational processing envelope protein F is synthesizied within an infected cell, has been cleaved from the precursor protein (by cellular protease(s) to produce the virion disulfide-linked F1 and F2 subunits (amino F2-S-S-F1 carboxyl), during post-translational processing envelope protein modifications occur that include glycosylation, or disulfide cross-linking. Envelope protein G (Pneumovirus), or H (Morbilivirus), or HN (Paramyxovirus, has been sequenced, or a function assigned; is an attachment protein which possess(es) hemagglutination activity in all genera except Pneumovirus where it is called G protein. If the protein also contains neuraminidae activity as in the genus Paramyxovirus it is called HN; during post-translational processing envelope protein modifications occur that include glycosylation. Envelope protein has a molecular mass of 22000 Da. Envelope protein SH or A; is a small integral a membrane protein. Nucleocapsid protein N or NP has a molecular mass of about 50000 Da; is protecting of the genome; which possess(es) RNA-binding activity. Nucleocapsid protein P is found in the virion in about 10-fold greater abundance than protein L; has a molecular mass of 40000-60000 Da; is polymerase associated and has has possibly a template melting function; modifications during post-translational processes include phosphorylation. Nucleocapsid protein L is large and; is a putative polymerase; which possess(es) RNA catalyzing activity in connection with protein P. Matrix protein M is an unglycosylated inner membrane protein. Non-Structural Proteins: Virus-coded non-structural proteins have been identified by sequence analysis and at least 6 non-structural protein(s) are found. The virus codes for enzymes. In addition to the polymerase, the virus codes for enzymes such as found variously expressed amomg the genera and include a RNA-dependent RNA transcriptase, adenylated transferase, mRNA guanylyl transferase, methyl-transferase, proteinase, and neuraminidase. The non-structural protein is associated with the membrane protein. Non-structural protein C. Non-structural protein NS1. Non-structural protein NS2. Non-structural protein V, a cystein rich protein,. Its role is zinc binding. Non-structural protein SH, a small integral membrane protein. Non-structural protein M2, formerly called 22-kDa. Its role is transcription processivity factor, which previously was thought to be a second M-like protein. Lipids Lipids are present and located in the envelope. Virions are composed of 20-25% 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. Carbohydrates Carbohydrates are found in virions; constitute 6% of virion dry weight; are present as glycoproteins; are N-linked glycans (side chains found in the fusion and attachment proteins), or O-linked glycosidic side chains (in the attachment protein G in the subfamily Pneumoviridae) and contain polylactosamine (in the SH protein of Respiratory syncytical virus). Carbohydrate composition in the virion is host-dependent. Genome Organization and Replication Virions attach to specific receptors located on the surface of cell membrane and enter host cells via fusion of the viral envelope with the host cell surface in an environment of neutral pH. Transcription: The viral genome is transcribed processively from the 3' end by virion-associated enzymes. The viral genome is transcribed by a viral associated enzymescanal is distinct; to 5-10 mRNA(s). The transcribed mRNAs are subgenomic in a viral-complementary sense. Transcription is guided by short (10-13 bp) conserved transcription start and termination/polyadenylation signals flanking each transcriptional element). The 5' ends of mRNAs are capped. The 3' ends of mRNAs possess a poly (A) tract (synthesized by reiterative copying of the polyadenylation site). Intergenic regions of viral genome may vary in size and sequence between genera ((Rubulavirus, Pneumovirus) or are highly conserved in sequence and length (Respirovirus, Morbilivirus)). Translation: The genome replicates in the cytoplasm. The parental genome does not serve as template. Replication is independent of host nuclear functions. Replication cycle Accumulations of virions in vitro are sensitive to amantadine. Assembly and Egress: Independently nucleocapsid. Maturation: The mature virus is found in the respiratory tract; skin. In thin sections the mature virus is seen in crystalline arrays. Nucleocapsids are enveloped at sites containing virus capsid proteins.
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landingpage: http://www.ncbi.nlm.nih.gov/bioproject/PRJNA16882
authentication:
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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