|CryoEM model of Enterobacteria phage PRD1 capsid. PDB entry |
|Group:||Group I (dsDNA)|
Tectivirus is a genus of viruses, and is currently the only genus in the family Tectiviridae. Gram-negative bacteria serve as natural hosts. There are currently four species in this genus including the type species Enterobacteria phage PRD1. Tectiviruses have no head-tail structure, but are capable of producing tail-like tubes of ~ 60×10 nm upon adsorption or after chloroform treatment. The name is derived from Latin tectus (meaning 'covered').
The virions of Tectiviridae species are non-enveloped, icosahedral and display a pseudo T=25 symmetry. The capsid has two layers. The outer layer is a protein structure of 240 capsid proteins trimers, and the inner one is a proteinaceous lipid membrane which envelopes the virus genome. Apical spikes extending about 20 nanometers (nm) protrude from the icosahedrons vertices.
The genome is a single molecule of linear double-stranded DNA of 15 kilobases in length, and has 30 open reading frames. It forms a tightly packed coil and encodes several structural proteins. It encodes about 30 proteins that are transcribed in operons. At least 9 structural proteins are present in the viron. The genome is about 66 megaDaltons in weight and constitutes 14–15% of the virion by weight. Lipids constitute a further 15% by weight. Carbohydrates are not present.
|Genus||Structure||Symmetry||Capsid||Genomic Arrangement||Genomic Segmentation|
Viral replication is cytoplasmic. Entry into the host cell is achieved by adsorption into the host cell. After adsorption to the host cell surface the virion extrudes a tail-tube structure through a vertex for genome delivery into the host. Replication follows the DNA strand displacement model. DNA-templated transcription is the method of transcription. Capsid proteins polymerize around a lipoprotein vesicle translocated in the cytoplasm by virion assembly factors.
Mature virons are released by lysis, which, in the case of PRD1, is achieved with the aid of virus-encoded lysis machinery consisting of four proteins: P15 (endolysin), P35 (holin), P36 and P37 (homologues of the Rz/Rz1 proteins of phage lambda).
|Genus||Host Details||Tissue Tropism||Entry Details||Release Details||Replication Site||Assembly Site||Transmission|
|Tectivirus||Gram-negative bacteria||None||Injection||Lysis||Cytoplasm||Cytoplasm||Passive diffusion|
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- 68.0.1. Tectivirus