Cereal Chem 42:71 - 85.  |  VIEW ARTICLE

Isolation and Characterization of the 7S Component of Soybean Globulins.

R. C. Roberts and D. R. Briggs. Copyright 1965 by the American Association of Cereal Chemists, Inc. 

A method is described for isolating a portion of the 7S fraction of the acid-precipitable soybean proteins, the globulins, as an approximately 90% ultracentrifugally pure preparation. Evidence is given that the 7S component, so isolated, is representative of the whole 7S fraction of the acid-precipitable protein. The amino acid analysis, carbohydrate content, and the N-terminal amino acids of the 7S fraction are compared with those reported for the whole globulin mixture.The 7S fraction undergoes a specific and characteristic 7S-9S isomerization under proper environmental conditions, and this reaction is shown by all of the 7S fraction of the total globulins. Molecular-weight determinations of the 7S and of the 9S forms verify that this isomerization is a dimerization. The pH and ionic strength dependence of the reaction implies that spatially specific electrostatic forces are involved. The sedimentation behaviors of the 7S entity in acidic, urea, and detergent solutions are presented. The retention of the ability of the treated protein to dimerize is taken as a criterion of reversibility and lack of denaturation during the treatment. Evidence for the existence of subunits of the 7S is presented.