Promoters of most seed proteins in legumes contain one or more 5'-CATGCAT-3' elements. To test if these elements have a function in the expression of these genes, the 2.3 kilobase pairs Gy2 glycinin promoter was ligated to a beta-glucuronidase reporter sequence and transformed into tobacco. Elimination of a 5'-CATGCAT-3' element 101 base pairs upstream from the transcription start site in the construction caused about a 10-fold reduction in the amount of beta-glucuronidase activity compared with when the element was present in the gene. Elimination of 1.9 kilobase pairs from the 5'-end of the promoter caused a two-to threefold reduction in activity. The results show that the 5'-CATGCAT-3' element plays a role in regulating the amount of expression from the gene, but that there are also other factors farther upstream from the gene that affect the level of expression.