β-Conglycinins in Developing Soybean Seeds

The temporal sequence of development of the major proteins of seeds of soybean (Merr.) has been studied during development of cotyledons from flowering to maturity. A well-defined difference occurred in the times of appearance and the periods of maximum accumulation of alpha, alpha'-, and beta-subunits of betaconglycinin. Whereas alpha- and alpha'-subunits appeared 15 to 17 days after flowering, accumulation of beta-subunit did not commence until 22 days after flowering. Such alterations in subunit composition infer that changes also occurred in the amino acid composition of betaconglycinin during maturation, particularly in the content of methionine which is low in the beta-subunit.