Eukaryotic Translation Initiation Factor 2 Subunit alpha

eIF-2a is a 36kD protein and is ubiquitously expressed in many cell types. The eIF-2 protein, which is composed of three subunits (alpha, beta and gamma), is one of the key molecules in the initiation of translation. The phosphorylation of eIF-2a is an important regulatory process in protein synthesis. In mammalian cells, eIF-2a is phosphorylated at serine 51 by at least two kinases: the heme-controlled repressor (HCR) and the interferon inducible double stranded RNA-dependent protein kinase (PKR). Phosphorylation of eIF-2a blocks the GDP-GTP exchange activity of eIF-2b, resulting in the suppression of protein synthesis.