Parvoviridae. Parvoviridae

Description of Parvoviridae adapted from ICTVdb Virion Properties Morphology Virions consist of a capsid. Virus capsid is not enveloped, round with icosahedral symmetry. The nucleocapsid is isometric and has a diameter of 18-22 nm, or 20-26 nm. Capsids appear round. The capsid consists of 60 capsomers, each a quadrilateral 'kite-shaped' wedge. Surface projections are small and surface appears rough and distinct spikes. Movie of reconstructed viruses can be found at movie of canine parvovirus particle, Institute of Molecular Virology, Madision Wisconsin; stero view of canine parvovirus particle, Institute of Molecular Virology, Madision Wisconsin. Physicochemical and Physical Properties Virions have a buoyant density in CsCl of 1.38-1.45 g cm-3. Nucleic Acid The genome is not segmented and contains a single molecule of linear negative-sense, or negative-sense and positive-sense, single-stranded DNA. The complete genome is 5000 nucleotides long. The genome has terminally redundant sequences. The genome sequence is repeated at one end, or repeated at both ends. Nucleotide sequences at the 3'-terminus are complementary to similar regions on the 5' end, or unrelated to the 5'-terminus. The 5'-terminal sequence has inverted repeats of the 3'-terminus, or palindromic repeats, forming a hairpin structure (if distinct from 3'-terminal sequence, terminal repeats at the 5'-end are 120-300 nucleotides long (and longer). The 3'-terminus has conserved nucleotide sequences; of 120-300 nucleotides in length (and longer, in species of same genus; sequence has palindromic arrangement (interrupted by two smaller internal palindromic sequences), or palindromic repeats, folding into a T- or Y-shaped structure. Populations of mature viruses contain particles with equivalent numbers of positive and negative sense ssDNA . Upon extraction, the complementary DNA strands usually form dsDNA. Proteins The viral genome encodes structural proteins. Lipids Lipids are absent. Translation: Virions are associated with helper virus, but independent from its functions during replication, or are associated with helper virus and dependent on co-infection of helper virus during replication.