Taxonomic Structure of the Subfamily
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Subfamily |
Pneumovirinae |
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Genus |
Pneumovirus |
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Genus |
Metapneumovirus |
Member species differ from those of the subfamily Paramyxovirinae in several features: (1) possession of 8-10 separate transcriptional elements; (2) smaller average ORF size; (3) possession of one additional unglycosylated nucleocapsid-associated protein (M2, formerly called 22K); (4) extensive O-linked glycosylation of the G protein; (5) the P locus encodes a single protein and does not have RNA editing; (6) a lack of amino acid sequence relatedness except for a low level in the F and L proteins, (7) the nucleocapsid diameter (13-14 nm compared with 18 nm in the subfamily Paramyxovirinae); (8) nucleocapsid pitch (7 nm); (9) length of glycoprotein spikes (10-14 nm). Species in the subfamily Pneumovirinae, genus Pneumovirus also lack neuraminidase; hemagglutinin is absent in BRSV and HRSV, but is present in Murine pneumonia virus (MPV). The G protein is structurally unrelated to the HN or H proteins of the other genera of the family Paramyxoviridae and exhibits a high level of interstrain diversity only 53% identity among HRSV isolates and only 21-30% identity between human and animal respiratory syncytial viruses.
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