TRAF5 preferentially interacts with the PKR kinase domain. (A) Schematic representation of PKR and the different mutant proteins used. Domains are as in Fig. 5C. (B) HeLa cells grown in 10-cm-diameter plates were infected with 5 PFU of VT7 per cell plus 5 PFU of VV per cell (lanes 1, 2, and 4), 5 PFU of VT7 per cell plus 5 PFU of VV TRAF5 per cell (lanes 3 and 5), 5 PFU of VV per cell plus 5 PFU of VV K296R per cell (lane 6), or 5 PFU of VV TRAF5 per cell plus 5 PFU of VV K296R per cell (lane 7). After 1 h, plasmids encoding PKR-C (10 μg) or PKR-N (10 μg) were transfected as indicated. Cell extracts were collected at 20 hpi, immunoprecipitated (IP) with anti-PKR or anti-FLAG serum, and thoroughly washed, and immunocomplexes were analyzed by SDS-PAGE and subjected to immunoblotting (Western blotting [WB]) with antiserum to PKR or FLAG. TBD, third basic domain.