Glycinin composition of several perennial species related to soybean

The 7S and 11S seed storage proteins from four perennials related to soybean (Glycine canescens, G. tomentella, G. tabacina, and G. clandestina) were analyzed by sodium dodecyl sulfate-gel electrophoresis. Each species yielded a unique electrophoretic pattern that varied in the total number of bands and their relative mobilities. In every case, the electrophoretic patterns were substantially different from CX635-1-1-1, the strain of G. max used in this study for comparison. Size heterogeneities among both the 7S and 11S polypeptides of the perennials were evident.

Abundant proteins in the 11S fraction from G. tomentella (CSIRO No. 1133) were separated by chromatography on DEAE-Sephadex and then their apparent molecular weights, amino acid compositions, and NH₂-terminal amino acid sequences were determined. A group of proteins were obtained which resembled the A_1b-polypeptide components of glycinin from G. max. They had the same size (M_r 37,000), identical NH₂-terminal sequences, and similar amino acid compositions to A_1b. A second group of acidic proteins (M_r 50,000) in G. tomentella had NH₂-terminal sequences homologous to the A₅ component (M_r 10,000) of glycinin. The latter group of polypeptides had a substantially higher apparent molecular weight than any acidic polypeptide components of glycinin analyzed previously. A third group of polypeptides purified from G. tomentella were the same size as basic polypeptides of glycinin and had homologus NH₂-terminal sequences. The results indicated that the perennials exhibit variability in their seed proteins at a level not found among the cultivars of G. max and G. soja and may be useful in studies concerning the origin and organization of genes involved in the synthesis of storage proteins in cultivated soybeans.