Transcriptional activator that binds to the DNA specific sequence 5'-GCCACGT[AC]AG-3' found in the alpha-globulin gene promoter (PubMed:9049271, PubMed:11572990). Does not bind to promoters of other major storage genes such as glutelin, prolamin and albumin (PubMed:9049271). Binds to the DNA specific sequence 5'-TGAGTCA-3' found in seed storage protein gene promoters (PubMed:11133985). Heterodimer with RISBZ1/BZIP58. Expressed in developing seeds from 5 to 30 days after flowering (DAF).