Molecular characterization, cloning and structural analysis of a cDNA encoding an amaranth globulin

A globulin from amaranth was extracted and purified by gel filtration and ultracentrifugation. The protein with molecular mass around 398 ku (kDa) showed by SDS-PAGE, under reductive conditions, polypeptides of 59, 36 and 24 ku. The N-terminal amino acids of 59 ku polypeptide were sequenced. A cDNA library was made from poly(A+) RNA isolated from developing amaranth seeds, and amaranth globulin cDNA clones were identified by hybridization with synthetic oligonucleotide designed from the N-terminal amino-acid sequence. Eight globulin clones were distinguished and two of them were sequenced, resulting in identical sequences. The deduced amino-acid sequence confirmed that the protein is synthesized as a precursor similar to other 11S-like proteins, suggesting that amaranth globulins could have the same ancestral gene common to dicot and monocot species.