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.