Organization of the sunflower 11S storage protein gene family

We have isolated and characterized genes encoding the sunflower US globulin seed storage proteins, collectively termed helianthinin. One gene, designated HaG3 has a primary transcription unit of about 1750 nucleotides including two short intervening sequences. The predicted precursor polypeptide from HaG3 is 493 amino acids long, is rich in glutamine and other nitrogen-rich amino acids and includes the amino acid sequence NGVEETICS. This sequence is highly conserved among 11S seed storage proteins and is involved in the proteolytic processing of these polypeptides. Additional helianthinin sequences are conserved among other seed storage protein genes. Analysis of various cDNA and genomic sequences indicates helianthinins are encoded by a small gene family that includes a minimum of two divergent subfamilies.