SOYBEAN SEED 34-KDA OIL-BODY-ASSOCIATED PROTEIN SEPARATED BY 2-DIMENSIONAL GEL-ELECTROPHORESIS

In soybean (Glycine spp.), a major seed cotyledon protein was identified by two-dimensional gel electrophoresis. Having an isoelectric point of 4.0 and relative molecular mass of 34 000, it consisted of about 5% of the total seed cotyledon protein in variety Miyagishirome, and was designated as 34-kDa protein in this study. The N-terminal amino acid sequence of the 34-kDa protein was determined as KKMKKEQYSC DHPPASWDWR KKGVITQ. There was at least one intra-disulfide bond, but no N-linked oligosaccharide chain in the molecule. The 34-kDa protein was immunologically detected the ninth day after flowering. In the early stages of seed development, the protein was observed as polymerised molecules. Based on these results, the 34-kDa protein was considered identical to the oil-body-associated protein recently reported (Karinski et al., J. Biol. Chem., 265 (1990) 13843). The relationship between amounts of lipids and 34-kDa protein in the seed cotyledons was analyzed and a significant positive correlation (r = 0.94) was found.