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J. Virol., 08 1995, 5195-5198, Vol 69, No. 8
DC Thomis and CE Samuel
The interferon-inducible, RNA-dependent protein kinase (PKR) is activated
by autophosphorylation, a process mediated by double-stranded RNA. A
catalytically deficient, histidine-tagged mutant PKR protein
[His-PKR(K296R)] was used as the substrate for characterization of the
intermolecular phosphorylation catalyzed by purified wild-type PKR
[PKR(Wt)]. The intermolecular autophosphorylation of His-PKR(K296R) by
PKR(Wt) was RNA dependent. Excess His-PKR(K296R) substrate inhibited both
the auto- and the trans-phosphorylation activities of PKR(Wt). Inhibition
of PKR(Wt) by His-PKR(K296R) was relieved by higher concentrations of
activator double-stranded RNA. Phosphopeptide analysis revealed that the
sites of intermolecular autophosphorylation in His-PKR(K296R) were very
similar, if not identical, to the sites that were autophosphorylated in
PKR(Wt) and suggest a multiple of four major phosphorylation sites per PKR
molecule.
Copyright © 1995, American Society for Microbiology
Mechanism of interferon action: characterization of the intermolecular autophosphorylation of PKR, the interferon-inducible, RNA-dependent protein kinase
Department of Biological Sciences, University of California, Santa Barbara 93106, USA.
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