Acts as a positive activator of the gcn2 protein kinase activity in response to amino acid starvation. Forms a complex with eif2ak4/gcn2 on translating ribosomes; during this process, gcn1 seems to act as a chaperone to facilitate delivery of uncharged tRNAs that enter the A site of ribosomes to the tRNA-binding domain of eif2ak4/gcn2, and hence stimulating eif2ak4/gcn2 kinase activity. Participates in the repression of global protein synthesis and in gene-specific mRNA translation activation, such as the transcriptional activator atf4, by promoting the eif2ak4/gcn2-mediated phosphorylation of eukaryotic translation initiation factor 2 (eIF-2-alpha/eif2s1) on 'Ser-53', and hence allowing atf4-mediated reprogramming of amino acid biosynthetic gene expression to alleviate nutrient depletion. Interacts with eif2ak4/gcn2; this interaction stimulates the eif2ak4/gcn2 kinase activity and is impaired by impact upon a variety of stress conditions, such as amino acid depletion, UV-C irradiation, proteasome inhibitor treatment and glucose deprivation. Interacts with impact; this prevents the interaction of gcn1 with eif2ak4/gcn2 and inhibits eif2ak4/gcn2 kinase activity. Belongs to the GCN1 family.