Molecular biology
VIRION
Non enveloped, icosahedral virion with a pseudo T=25 symmetry, consisting of 240 capsid proteins trimers. Virion size is about 66 nm with apical spikes of 20 nm.
The capsid encloses a inner membrane vesicle within which the genomic DNA is coiled.
GENOME
Linear, dsDNA genome of about 15 kb flanked by inverted repeats. Encodes for 30 ORFs. Replication is protein-primed.
GENE EXPRESSION
Genes are transcribed by operons.
REPLICATION
CYTOPLASMIC
- Adsorption: the phage attaches to target cell through its spikes.
- Internal phage membrane transforms into a tubular structure that protrudes through a vertex and penetrates the host cell membrane for DNA injection
- Transcription and traduction of early genes
- Replication of genomic DNA
- Transcription and traduction of late genes
- Capsid proteins polymerize around a lipoprotein vesicle translocated in the cytoplasm by virion assembly factors.
- Genomic DNA is packaged in new virions
- Mature virions are released from the cell by lysis