Detection and characterization of a new β-conglycinin from soybean seeds

A new protein has been isolated from the reserve proteins of the seeds of soybean ( Glycine max) which is particularly deficient in methionine and cysteine. The protein dissociated in sodium dodecyl sulfate into a single polypeptide, M r 48,000. The amino acid composition, N-terminal leucine and mobility on gel electrophoresis of this polypeptide all were indistinguishable from the β-subunit of β-conglycinin. In its nondissociated form, the protein behaved as a trimer of M r, 137,000 ± 4000. Its sedimentation coefficient at ionic strength 0.5 was 7.5 S and it possessed antigenic determinants in common with β-conglycinin. This protein therefore has the properties of a new isomer of β-conglycinin—a homogeneous trimer of β subunits.