VIRION
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Non-enveloped, head-tail structure. Heads are about 84-94 nm in diameter and and tails 140-219 in length. The tail is contractile with globular structures at its tip, has 6 long terminal fibers, 6 short spikes and a double base plate. The capsid has a T=16 symmetry (SPO1-like viruses).
GENOME
Linear, dsDNA genome of 130-140 kb, encoding for about 190-215 proteins.
GENE EXPRESSION
Genes are transcribed by operons. Some Twortvirus might have circularly permuted genomes.
ENZYMES
- DNA-directed DNA polymerase family A palm
- Cysteine protease (Peptidase C51)
- Ribonucleoside reductase
REPLICATION
CYTOPLASMIC
- Adsorption: the phage attaches to the target cell through its tail fibers.
- Ejection of the viral DNA into host cell cytoplasm by contraction of the tail sheath.
- Transcription and translation of early genes.
- Replication of genomic DNA. Transcription and translation of late genes.
- Assembly of an empty procapsid and packaging of the genome.
- Viral tail fibers assembly and viral tail assembly.
- Mature virions are released from the cell by lysis.