Assembly of Qβ viral RNA polymerase with host translational elongation factors EF-Tu and -Ts
2010
Takeshita, Daijiro | Tomita, Kozo
Replication and transcription of viral RNA genomes rely on host-donated proteins. Qβ virus infects Escherichia coli and replicates and transcribes its own genomic RNA by Qβ replicase. Qβ replicase requires the virus-encoded RNA-dependent RNA polymerase (β-subunit), and the host-donated translational elongation factors EF-Tu and -Ts, as active core subunits for its RNA polymerization activity. Here, we present the crystal structure of the core Qβ replicase, comprising the β-subunit, EF-Tu and -Ts. The β-subunit has a right-handed structure, and the EF-Tu:Ts binary complex maintains the structure of the catalytic core crevasse of the β-subunit through hydrophobic interactions, between the finger and thumb domains of the β-subunit and domain-2 of EF-Tu and the coiled-coil motif of EF-Ts, respectively. These hydrophobic interactions are required for the expression and assembly of the Qβ replicase complex. Thus, EF-Tu and -Ts have chaperone-like functions in the maintenance of the structure of the active Qβ replicase. Modeling of the template RNA and the growing RNA in the catalytic site of the Qβ replicase structure also suggests that structural changes of the RNAs and EF-Tu:Ts should accompany processive RNA polymerization and that EF-Tu:Ts in the Qβ replicase could function to modulate the RNA folding and structure.
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