Seed storage protein. Accumulates during seed development and is hydrolyzed after germination to provide a carbon and nitrogen source for the developing seedling. The alpha-, alpha'-, and beta-subunits associate in various combinations to form trimeric proteins. Localizes in protein storage vacuoles in cotyledons of developing and mature beans (PubMed:15447650, Ref.6). Synthesized and assembled into trimers in the endoplasmic reticulum, and transported to the protein storage vacuoles by the dense vesicles (PubMed:15447650). Expressed in seeds. Not detected in cotyledons or in mature plants. Expressed early in embryogenesis, with a high transcription rate at midmaturation and then decreases prior to seed dormancy. The N-linked glycans are not essential for the folding and assembly into trimers. Causes an allergic reaction in human (PubMed:18996574). Binds to IgE of patients with severe allergic reactions (anaphylaxis) to soybean (PubMed:18996574). Mutagenesis of Ile-145 and Lys-147 allow the creation of a beta-conglycinin beta chain containing a phagocytosis-stimulating peptide, soymetide, found normally only in the alpha' chain. The three mutants created exhibit phagocytosis activities after digestion by trypsin and the order is wild type < I145M/K147T < I145M/K147F < I145M/K147W. Belongs to the 7S seed storage protein family.