Functions in the early steps of protein synthesis by forming a ternary complex with GTP and initiator tRNA. This complex binds to a 40S ribosomal subunit, followed by mRNA binding to form a 43S pre-initiation complex. Junction of the 60S ribosomal subunit to form the 80S initiation complex is preceded by hydrolysis of the GTP bound to eIF-2 and release of an eIF-2-GDP binary complex. In order for eIF-2 to recycle and catalyze another round of initiation, the GDP bound to eIF-2 must exchange with GTP by way of a reaction catalyzed by eIF-2B. EIF2S1/eIF-2-alpha is a key component of the integrated stress response (ISR), required for adaptation to various stress: phosphorylation by metabolic-stress sensing protein kinases (EIF2AK1/HRI, EIF2AK2/PKR, EIF2AK3/PERK and EIF2AK4/GCN2) in response to stress converts EIF2S1/eIF-2-alpha in a global protein synthesis inhibitor, leading to a attenuation of cap-dependent translation, while concomitantly initiating the preferential translation of ISR-specific mRNAs, such as the transcriptional activators ATF4 and QRICH1, and hence allowing ATF4- and QRICH1-mediated reprogramming. Activity is regulated by phosphorylation at Ser-49 and Ser-52, which stabilizes the eIF-2/GDP/eIF-2B complex and prevents the eIF-2B-mediated exchange of GDP for GTP, thereby preventing the formation of the 43S pre-initiation complex (PIC). This results in the global attenuation of 5' cap-dependent protein synthesis and concomitant translation of ISR-specific mRNAs that contain a short upstream open reading frame (uORF) in their 5' UTR, such as ATF4, ATF5, DDIT3/CHOP and PPP1R15A/GADD34. Heterotrimer composed of an alpha, a beta and a gamma chain (By similarity). Component of an EIF2 complex at least composed of CELF1/CUGBP1, CALR, CALR3, EIF2S1, EIF2S2, HSP90B1 and HSPA5. Interaction with METAP2 protects EIF2S1 from inhibitory phosphorylation (By similarity). Interacts with ABCF1 isoform 2. Associates with ribosomes. Interacts with DDX3X in an RNA-independent manner (By similarity). Colocalizes with NANOS3 in the stress granules. Phosphorylation at Ser-49 and Ser-52 stabilizes the eIF-2/GDP/eIF-2B complex and prevents GDP/GTP exchange reaction, thus impairing the recycling of eIF-2 between successive rounds of initiation and leading to global inhibition of translation, while concomitantly initiating the preferential translation of integrated stress response (ISR)-specific mRNAs (By similarity). Substrate for at least 4 kinases: EIF2AK1/HRI, EIF2AK2/PKR, EIF2AK3/PERK and EIF2AK4/GCN2. Phosphorylated; phosphorylation on Ser-52 by the EIF2AK4/GCN2 protein kinase occurs in response to amino acid starvation and UV irradiation (By similarity). Belongs to the eIF-2-alpha family. This gene should not be confused with EIF2A, with which it shares the alias EIF2A. Although both of these proteins function in binding initiator tRNA to the 40S ribosomal subunit, the eIF2 complex requires GTP, whereas the EIF2A protein does so in a codon-dependent manner.