Fig. 1. Expression of a GST–PKR kinase domain fusion protein, but not the isolated kinase domain alone, is toxic in yeast. (A) Schematics of wild-type human PKR [PKR (wt)] showing two dsRNA binding domains (dsRBDs) in the N-terminal half of the protein and the kinase domain (residues ∼263–551) in the C-terminal half of the protein; the isolated PKR kinase domain [PKR (258–551)]; and a GST–PKR kinase domain fusion protein (GST–PKR). (B) Plasmids expressing wild-type PKR (p1420), PKR-K296H (p1421), the isolated PKR kinase domain [PKR (258–551); pC681], or the GST–PKR kinase domain fusion protein (pC661), as indicated, under the control of a yeast GAL-CYC1 hybrid promoter were introduced into strain J80 containing wild-type eIF2α and strain J82 containing eIF2α-S51A, as indicated. Trans formants were streaked on SGal medium (synthetic minimal medium containing 10% galactose) supplemented with essential nutrients, and the plates were incubated at 30°C for 6 days.