Subunit structure and immunological properties of a basic 7s globulin from soybean seeds

Abstract

Basic 7S globulin from defatted soybean (var. Miyagishirome) meal was isolated from the 0.5 M NaCl-soluble fraction by ion-exchange chromatography on CM-Sepharose CL-6B. The basic 7S globulin was distinguished immunologically from the other soybean proteins. SDS—urea gel electrophoresis of basic 7S globulin gave two kinds of subunits ( M, 16 000 and 26 000), designated as LMWS (low M, subunit) and HMWS (high M, subunit), respectively, in the presence of a 2-mercaptoethanol (2-ME)-containing system. They gave only one intermediary subunit ( M, 42 000) without 2-ME. Two kinds of HMWS (H-I and H-II) and two kinds of LMWS (L-I and L-II) were separated by polyacrylamide gel electrophoresis in a urea-acetic acid system. The basic 7S globulin was fractionated into two components (designated as basic 7S-I and basic 7S-II) on CM-Sepharose CL-6B. The subunits of basic 7S-I and basic 7S-II comprising H-I and L-I, and H-II and L-II, respectively.