Purification and Characterization of the Acid Soluble 26-kDa Polypeptide from Soybean Seeds

Abstract

Whey proteins from soybean seeds of Japanese varieties were analyzed by SDS–polyacrylamide gel electrophoresis (SDS–PAGE). Among 11 varieties of soybean, three green and one black soybeans lacked a 26-kDa band that was found in all yellow soybeans. In this paper, the 26-kDa protein was named AS26k (acid soluble 26-kDa protein) temporarily. The AS26k protein was purified from Glycine max cv. Nattosyoryu, which is yellow soybean, through four purification steps: 30–35% saturated ammonium sulfate fractionation, ion exchange chromatography on S Sepharose Fast Flow, gel filtration on Sephadex G-100, and hydrophobic chromatography on phenyl Sepharose CL-4B. Purified AS26k was cleaved with V8 proteinase from Staphylococcus aureus or CNBr. The cleaved polypeptide contained two typical dehydrin motif sequences: DEYGNPV and (M)DKIKEKLPG, and a 19 amino acids sequence similar to a pea dehydrin. Native AS26k had a molecular mass of 32 kDa on gel filtration and a pI of 7.2 on two-dimensional PAGE. Similarly to other dehydrins and late embryogenesis abundant (LEA) proteins, AS26k was rich in hydrophilic amino acids, and highly heat stable. These results showed that AS26k was a dehydrin, a group II LEA protein in soybean seeds. © 1997, Taylor & Francis Group, LLC. All rights reserved.