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RNA-dependent Protein Kinase Activation: Viral Defense

The RNA-dependent protein kinase (PKR) plays a vital role in antiviral defense in response to cellular infection and thus is the subject of much interest. PKR responds to viral genomic contamination within the host cell by phosphorylating eukaryotic initiation factor 2, which results in the inhibition of translation initiation. The kinase contains three distinct domains: a C-terminal kinase domain, a central linker, and two N-terminal domains, which bind double-stranded RNA (dsRNA). However, the manner in which these domains function together for signal transduction has remained uncertain.

A model for the activation of PKR.

In this Paper of the Week, Sean A. McKenna and colleagues combine nuclear magnetic resonance spectroscopy, dynamic light scattering, gel filtration, and autophosphorylation kinetics to provide a new and coherent view of the RNA activation of the latent enzyme. The authors propose that in a series of steps, RNA binding leads to PKR dimerization and autophosphorylation, followed by RNA release and activation of the enzyme for substrate phosphorylation.

FOOTNOTES

See referenced article, J. Biol. Chem. 2007, 282, 11474-11486

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