EIF-2 kinase

There are two mammalian eIF-2 alpha kinases, the double-stranded RNA-dependent kinase (PKR) and heme-regulated inhibitor kinase (HRI), both of which are responsible for the phosphorylation of the alpha subunit of eIF-2 at serine 51, one of the best-characterized mechanisms for down-regulating protein synthesis in higher eukaryotes in response to various stress conditions.