Alpha subunit of translation initiation factor eIF2B (eIF2Bα); guanine-nucleotide exchange factor for eIF2; mutations in eIF2Bα alter localization of eIF2B; activity regulated by phosphorylated eIF2; positive regulator of GCN4 expression; mutations in human ortholog EIF2B2 cause fatal brain disease childhood ataxia with central nervous system hypomyelination (CACH); human ortholog EIF2B1 can complement yeast null mutant