Mechanism of interferon action: characterization of the intermolecular autophosphorylation of PKR, the interferon-inducible, RNA-dependent protein kinase.
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.
Thomis
D C
DC
Department of Biological Sciences, University of California, Santa Barbara 93106, USA.
Samuel
C E
CE
D002851:Chromatography, High Pressure Liquid; D004790:Enzyme Induction; D006639:Histidine / Q000737:chemistry; D007372:Interferons / Q000378:metabolism / Q000502:physiology*; D007700:Kinetics; D010449:Peptide Mapping; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D019892:eIF-2 Kinase
D006639:Histidine; D007372:Interferons; D017346:Protein Serine-Threonine Kinases; D019892:eIF-2 Kinase