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The viral genome is a linear double-stranded DNA molecule with inverted terminal repeat sequences bound by terminal proteins, and contains a gene encoding a putative type B DNA polymerase (Bath et al., 2006).
Virions are ~70 nm in diameter and pleomorphic in shape with a membrane vesicle and irregularly distributed spike structures. Virions contain a single type of internal membrane protein (VP27), two types of spike protein (VP28 and VP29), as well as protein VP32 with unknown function (Pietilä et al., 2012).
Virions have a buoyant density of about 1.30 g cm−3 in CsCl (Bath et al., 2006). Virions are stable at pH 6-9, and high NaCl concentration (above 2.5 M), but are readily inactivated by low NaCl concentrations or the absence of NaCl, low pH, temperatures above 50 °C, organic solvents, or detergents (Bath et al., 2006).
The virion DNA of the gammapleolipovirus His2 virus (His2) is a linear double-stranded molecule of about 16 kbp with inverted terminal repeat sequences bound by terminal proteins (Bath et al., 2006).
Virions contain three major structural proteins: internal membrane protein VP27, and two spike proteins, VP28 and VP29. An additional structural protein, VP32, with an unknown function, has been identified and shares no homologues with the members of the other genera (Pietilä et al., 2012, Senčilo et al., 2012).
Virions contain lipids derived non-selectively from host cell membranes. The major lipid species are PG, PGP-Me and PGS (Pietilä et al., 2012). The spike protein VP28 of His2 contains a lipid modification (Pietilä et al., 2012).
According to the genome organization and content, His2 is the most divergent member of the family Pleolipoviridae. Similarly to other members of the Pleolipoviridae, His2 contains the conserved cluster of five ORFs, albeit with small deviation. The His2 internal membrane protein VP27, encoded within the conserved ORF cluster, is not a homologue of internal membrane proteins of other pleolipoviruses, based on amino acid sequence similarity. However, it has an analogous function in the virion, i.e. it can be considered a functional homologue (Pietilä et al., 2012). Similarly to other Pleolipoviridae members, His2 has a non-lytic life cycle and is thought to exit host cell via budding (Pietilä et al., 2012, Svirskaitė et al., 2016).
His2 infects only its original isolation host Haloarcula hispanica (ATCC 33960) belonging to the family Haloarculaceae (Bath et al., 2006).
His2 was isolated from Pink Lakes in Victoria, Australia (Bath et al., 2006), while its host Haloarcula hispanica (ATCC 33960) originates from Spain.
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