Non-enveloped, spherical virion about 26 nm in diameter with T=3 icosahedral symmetry composed of 178 CP proteins 889 dimers) and a single A2 maturation protein .


Monopartite, linear, ssRNA(+) genome about 4 kb in size. The 5’ end is capped. Encodes 4 proteins.


The virion RNA is infectious and serves as both the genome and viral messenger RNA. Encodes for 4 ORFs. Cp protein repress replicase translation by binding a RNA hairpin at the start site of this gene. Lysis protein is expressed by suppression of termination of an UGA nonsense codon in levivirus genus (readthrough).


  1. Adsorption to F pili of target cells induces cleavage and release of the maturation protein.
  2. Genomic RNA enters the bacterium.
  3. Viral proteins are translated.
  4. Viral replicase assembles with host proteins (ribosomal protein S1, translation elongation factors EF-Tu and EF-Ts) to form the active RNA polymerase.
  5. Replication of genomic RNA into a minus strand, which serves as template to produce new positive strand genomes.
  6. Late in infection CP protein bind to a RNA hairpin on the genome, and new virus particles are assembled in the cytoplasm.
  7. Release by cell lysis.

Matching UniProtKB/Swiss-Prot entries

12 entries grouped by strain (browse by keywords)

4 entries

Enterobacteria phage MX1 (Bacteriophage MX1) reference strain

Select_all Deselect_all  
A1_BPMX1Minor capsid protein A1
CAPSD_BPMX1Capsid protein (CP) (Coat protein)
MATA2_BPMX1Maturation protein A2 (MP) (A2) (Assembly protein) (A protein)
RDRP_BPMX1RNA-directed RNA polymerase subunit beta (EC (RNA replicase beta ...

4 entries

Enterobacteria phage SP (Bacteriophage SP) reference strain

Select_all Deselect_all  
A1_BPSPMinor capsid protein A1
CAPSD_BPSPCapsid protein (CP) (Coat protein)
MATA2_BPSPMaturation protein A2 (MP) (A2) (Assembly protein) (A protein)
RDRP_BPSPRNA-directed RNA polymerase subunit beta (EC (RNA replicase beta ...

4 entries

Escherichia phage Qbeta (Bacteriophage Q-beta)

Select_all Deselect_all  
A1_BPQBEMinor capsid protein A1 (A1 read-through protein)
CAPSD_BPQBECapsid protein (CP) (Coat protein)
MATA2_BPQBEMaturation protein A2 (MP) (A2 protein)
RDRP_BPQBERNA-directed RNA polymerase subunit beta (EC (RNA replicase beta ...