Acts as a positive activator of the gcn2 protein kinase activity in response to amino acid starvation. Component of the gcn1-gcn20 complex that forms a complex with 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 gcn2, and hence stimulating gcn2 kinase activity. Participates in the repression of global protein synthesis and in gene-specific mRNA translation activation, such as the transcriptional activator fil1, by promoting the gcn2-mediated phosphorylation of eukaryotic translation initiation factor 2 (eIF-2-alpha/tif211) on 'Ser-52', and hence allowing fil1-mediated reprogramming of amino acid biosynthetic gene expression to alleviate nutrient depletion. Interacts (via N- and C-terminus) with gcn2 (via N-terminal RWD domain); this interaction stimulates gcn2 kinase activity in a gcn20-dependent manner in response to amino acid starvation. Interacts (via C-terminus) with gcn20 (via N-terminus); this interaction stimulates gcn2 kinase activity in response to amino acid starvation. The gcn1-gcn20 complex interacts with gcn2 on translating ribosomes in amino acid-starved cells; gcn1 may bind near the ribosomal A-site and promotes the transfer of uncharged tRNAs from the A-site to the tRNA-binding domain in gcn2 for its subsequent kinase activation, and hence allowing fil1 translational activation and derepression of amino acid biosynthetic genes. Interacts (via C-terminus) with yih1 (via N-terminus); this interaction reduces the gcn1-gcn20 complex formation and prevents the interaction of gcn1 with gcn2 and gcn2 kinase activation in amino acid-starved cells. The EF3-like region is necessary and sufficient for interaction with gcn20. Belongs to the GCN1 family.