''Portogloboviridae'' is a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

DNA viruses A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase. They can be divided between those that have two strands of DNA in their genome, called double-stranded DNA (dsDNA) viruses, and ...

that infect

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

. It is a proposed family of the

realm A realm is a community or territory over which a sovereign rules. The term is commonly used to describe a monarchical or dynastic state. A realm may also be a subdivision within an empire, if it has its own monarch, e.g. the German Empire. Etym ...

Varidnaviria ''Varidnaviria'' is a realm of viruses that includes all DNA viruses that encode major capsid proteins that contain a vertical jelly roll fold. The major capsid proteins (MCP) form into pseudohexameric subunits of the viral capsid, which stores t ...

''. Viruses in the family are related to '' Halopanivirales''.The references cited in this article refer to ''Sphaerolipoviridae''. In 2020, this family was split into three families within the order ''Halopanivirales'', so "''Halopanivirales''" is used throughout this article where sources state "''Sphaerolipoviridae''". The

capsid proteins A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...

of these viruses and their characteristics are of evolutionary importance for the origin of the other ''Varidnaviria'' viruses since they seem to retain primordial characters.

Description

The

virion A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

s in this family have a capsid with icosahedral geometry and a

viral envelope A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encase ...

that protects the

genetic material Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cla ...

. The diameter is 83 to 87 nanometers. The

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...

is circular and of double-stranded DNA with a length of 20,222 base pairs. The

contains 45

open reading frames In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible readin ...

(ORFs), which are closely arranged and occupy 89.1% of the genome. ORFs are generally short, with an average length of 103

codon The genetic code is the set of rules used by living cells to translate information encoded within genetic material ( DNA or RNA sequences of nucleotide triplets, or codons) into proteins. Translation is accomplished by the ribosome, which links ...

s. Virions have 10

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

ranging from 20 to 32 kDa. Of these proteins, 8 code for the capsid and two for the viral envelope, including one that is a vertical single jelly roll (SJR) capsid protein. Entry into the host cell is by penetration.

Viral replication Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome an ...

occurs by chronic infection without a

lytic cycle The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacter ...

. The ''Portogloboviridae'' viruses together with ''Halopanivirales'' have evolutionary importance in the evolution of the other ''Varidnaviria'' viruses since they appear to be relics of how the first viruses of this realm were. ''Portogloboviridae'' together with ''Halopanivirales'' may have infected the

last universal common ancestor The last universal common ancestor (LUCA) is the most recent population from which all organisms now living on Earth share common descent—the most recent common ancestor of all current life on Earth. This includes all cellular organisms; t ...

(LUCA) and originated before that organism. It has been proposed that it may be related to the origin of ''Varidnaviria'' in the following way.

Taxonomy

The family has one genus which has two species: * ''Alphaportoglobovirus'' ** '' Alphaportoglobovirus SPV2'' ** '' Sulfolobus alphaportoglobovirus 1''

Notes

References

{{Taxonbar, from=Q54811030 DNA viruses