Bacteriophage Qbeta
Qubevirus durum | |
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E. coli and its genome
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Virus classification ![]() | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Lenarviricota |
Class: | Leviviricetes |
Order: | Norzivirales |
Family: | Fiersviridae |
Genus: | Qubevirus |
Species: | Qubevirus durum
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Member viruses | |
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Bacteriophage Qbeta (Qubevirus durum), commonly referred to as Qbeta or Qβ, is a species consisting of several strains of
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/65/Leviviridae_virion.png/220px-Leviviridae_virion.png)
Genetics
The genome of Qβ is approximately 4,217 nucleotides, depending on the source which sequenced the virus. Qβ has been isolated all over the world, multiple times, with various subspecies that code for nearly identical proteins but can have very different nucleotide sequences.[citation needed]
The genome has three
Coat protein A1
There are approximately 178 copies of the coat protein and/or A1 in the capsid.[citation needed]
Replicase/RdRp
The RNA-dependent RNA polymerase that replicates both the positive and negative RNA strands is a complex of four proteins: the catalytic beta subunit (replicase, P14647) is encoded by the phage, while the other three subunits are encoded by the bacterial genome: alpha subunit (ribosomal protein S1), gamma subunit (EF-Tu), and delta subunit (EF-Ts).[3]
The structure of the Qbeta
Maturation/lysis protein A2
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/1-s2.0-S0022283615006762-gr1-C.jpg/220px-1-s2.0-S0022283615006762-gr1-C.jpg)
All positive-strand RNA phages encode a maturation protein, whose function is to bind the host
In bacteriophage MS2, the maturation protein is called the A protein, as it belongs to the first open reading frame in the viral RNA. In Qβ the A protein was initially thought to be A1, as it is more abundant within the virion and is also required for infection.[8] However, once the sequence of Qβ was determined, A1 was revealed to be a readthrough of the leaky stop codon.[citation needed]
A2 is the maturation protein for Qβ and has an additional role of being the lysis protein.[9]
The mechanism of lysis is similar to that of penicillin; A2 inhibits the formation of peptidoglycan by binding to MurA, which catalyzes the first enzymatically committed step in cell wall biosynthesis.[10]
Experiments
RNA from Bacteriophage Qβ was used by Sol Spiegelman in experiments that favored faster replication, and thus shorter strands of RNA. He ended up with Spiegelman's Monster, a minimal RNA chain of only 218 nucleotides that can be replicated by Qβ replicase.[11]