Amino Acid Sequencing and cDNA Cloning of Rice Seed Storage Proteins, the 13kDa Prolamins, Extracted from Type I Protein Bodies.

Abstract

The 13kDa prolamins, one of the rice storage proteins, consist of complex mixtures of polypeptides encoded by multigene family that show heterogeneity both in size and solubility. Although many researchers have isolated prolamin cDNA clones, it has not been possible to correlate most of these cDNA clones with individual 13kDa prolamin mature polypeptides. We isolated three new prolamin cDNA clones, λRM1, λRM4 and λRM9. Further more, we purified six 13kDa prolamin polypeptides from rice type I protein bodies, and determined these amino acid sequences. Here we demonstrate a classification for the 13kDa prolamin polypeptides which can be divided four classes, 13-I, 13-IIa, 13-IIb and 13-III. Cysteine labeling of the prolamin polypeptides indicated that 13-I contains cysteine residues, but 13-IIa or 13-IIb have no Cysteine residues. The 13-I polypeptide was soluble in nonreducing solution when their cysteine residues form inteamolecular disulfide bonds, but not soluble at intermolecular bonding.