This mechanism is also used by plant legumins. Furthermore is the newly synthesized polypeptide chain proteolytically cleaved into two parts linked by a disulfide bond. One is acidic and one basic. A similar situation is known to exist with insulin. They, too, are constructed from several polypeptide chains that are united by a quaternary structure.
All chains are cleavage products of one primary gene product.
Prolamines, the storage proteins of gramineae, are characterized by a high proportion of proline and glutamine. They are soluble in alcohol. They do also have a signal sequence but in contrast to legumines and vicelines is the polypeptide chain not cleaved. They are the products of a number of around 30-100 genes. Contrary to the genes of the leguminose storage proteins do they not contain introns, i.e. each gene consists of one undivided translated DNA chain.