Regulation of protein synthesis in reticulocyte lysates: immune serum inhibits heme-regulated protein kinase activity and differentiates heme-regulated protein kinase from double-stranded RNA-induced protein kinase.

Abstract

A specific immune serum to the heme-regulated inhibitor (HRI) was prepared by immunizing chickens with highly purified reversible HRI prepared from rabbit reticulocyte lysates. Studies with this immune serum demonstrated that the behavior of purified reversible HRI was similar to that of the inhibitor activated in rabbit reticulocyte lysates. The immune serum inhibited the phosphorylation of the small subunit (38,000 daltons) of the eukaryotic initiation factor eIF-2 by crude and purified inhibitor preparations prevented the concomitant inhibition of protein synthesis by crude and purified inhibitor preparations and prevented the autophosphorylation of the 95,000 dalton polypeptide in purified and crude HRI preparations. The protein kinase and inhibitory activities of crude and partially purified preparations of the double-stranded RNA-induced inhibitor of protein synthesis were not affected by the immune serum prepared to reversible HRI. The inhibitor induced by double-stranded RNA is apparently antigenically distinct from the reversible HRI.