The purification and partial amino acid sequence of a polypeptide from the glutelin fraction of rice grains; homology to pea legumin

AbstractThe glutelin fraction was extracted from grain meals of rice (Oryzea sativa) with 50 mM Tris-HCl buffer (pH 8.8) containing 6 M urea and 10 mM 2-mercaptoethanol. Polypeptides of glutelin were separated and purified by ion-exchange chromatography under denaturing conditions. Analysis by two-dimensional gel electrophoresis showed that 2 major polypeptides of the rice glutelin fraction, Mr 36 000 and 22 000, were linked in disulphide bonded pairs containing one Mr 36 000 and one Mr 22 000 subunit. A partial amino acid sequence of the purified Mr 22 000 glutelin subunit showed it to be homologous to the β-subunit of pea legumin, a storage protein which also contains disulphide-linked subunit pairs (Mr 38 000 and Mr 22 000). It is therefore proposed that the major component of rice glutelin is a legumin-like protein