Notes on Family: Paramyxoviridae
enveloped spheres
Contents
General Description
This family is characterised by its (usually) spherical, enveloped, particles at least 150nm in diameter, which contain a monopartite negative sense ssRNA genome of 15-18kb. It is classified in the order
Mononegavirales with three other families of enveloped viruses with monopartite negative sense genomes, i.e. the
Filoviridae (particles usually filamentous),
Bornaviridae (particles about 90 nm diameter) and
Rhabdoviridae (particles bullet-shaped).
Morphology
Virions pleomorphic but usually spherical, enveloped, 150 nm in diameter or larger with spike-like projections.
Genomen
Monopartite single-stranded negative sense RNA of 15-18 kb. There is no genome-linked protein (VPg) at the 5'-terminus nor a 3'-polyA tail. There are 6-10 transcriptional elements with the RNA polymerase at the 5'-end of the genome and the capsid nucleoprotein at or near the 3'-end. There is a fairly standard order of the major mRNAs (here listed in their order on the template strand - i.e. from 3' to 5' with respect to the virion strand):
- Coat protein (N)
- Phosphoprotein (P); a shorter non-structural protein (V) is produced from the same mRNA by members of the subfamily Paramyxovirinae and this involves a process of RNA editing; some genera produce a further non-structural protein (C) from a different reading frame of the same transcript
- Matrix protein (M)
- Fusion protein (F)
- Attachment protein which may be a Hemagglutinin (H) , Hemagglutinin-neuraminidase (HN) or Glycoprotein (G)
- Polymerase (L)
Genera in the Family
Classification is based on genome organisation and size and on the relatedness of the encoded proteins. Host type is sometimes also significant.
- Subfamily Paramyxovirinae, 6 or 7 transcriptional elements encoding 7-9 proteins
- Subfamily Pneumovirinae, 8-10 transcriptional elements encoding 9-11 proteins; there are no C or V proteins and no RNA transcript editing
