Malek-Hedayat S, Meiners S A, Metcalf T N, Schindler M, Wang J L, Ho S C
J Biol Chem. 1987 Jun 5;262(16):7825-30.
A lectin has been identified in the cell line, SB-1, originally derived from the roots of Glycine max. This lectin, which we shall refer to as SB-1 lectin, was isolated on the basis of its carbohydrate-binding activity (affinity chromatography on Sepharose column derivatized with N-caproyl-galactosamine) and its immunological cross-reactivity (immunoblotting with rabbit antibodies directed against seed soybean agglutinin (SBA]. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting analysis of SB-1 lectin revealed a major polypeptide (Mr approximately equal to 30,000) which co-migrated with seed SBA. This form of the lectin was observed in fractions purified from culture medium of SB-1 cells or supernatant fraction of SB-1 cell suspension after enzymatic removal of cell wall. Extracts of SB-1 cells under some other conditions yielded a major band (Mr approximately equal to 60,000) as revealed by SDS-PAGE and immunoblotting with rabbit anti-seed SBA; prolonged incubation of these samples in the presence of SDS resulted in the appearance of the 30-kDa polypeptide. It appears that the 60-kDa band represented a highly stable, even under SDS-PAGE conditions, dimeric form of the 30-kDa subunit. The SB-1 lectin derived from the culture medium was compared with seed SBA by gel filtration and by peptide mapping after limited proteolysis; no difference between the lectins from the two sources was found. Extracts of soybean roots fractionated on N-caproyl-galactosamine-Sepharose affinity columns yielded, upon elution with galactose, polypeptides of Mr 30,000 and 60,000. These results suggest that soybean roots contain a lectin whose polypeptide composition corresponds to that of seed SBA and SB-1 lectin.
在最初源自大豆根的细胞系SB - 1中已鉴定出一种凝集素。这种凝集素，我们将其称为SB - 1凝集素，是基于其碳水化合物结合活性（在经N - 己酰 - 半乳糖胺衍生化的琼脂糖柱上进行亲和层析）及其免疫交叉反应性（用针对种子大豆凝集素（SBA）的兔抗体进行免疫印迹）而分离得到的。对SB - 1凝集素进行十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳（SDS - PAGE）和免疫印迹分析显示，有一条主要多肽（Mr约等于30,000），它与种子SBA迁移位置相同。在从SB - 1细胞培养基中纯化的组分或酶解去除细胞壁后的SB - 1细胞悬液上清组分中观察到了这种凝集素形式。在其他一些条件下，SB - 1细胞提取物经SDS - PAGE和用兔抗种子SBA进行免疫印迹显示出一条主要条带（Mr约等于60,000）；在SDS存在下将这些样品长时间孵育会导致出现30 kDa的多肽。看来，即使在SDS - PAGE条件下，60 kDa的条带代表的是30 kDa亚基的一种高度稳定的二聚体形式。通过凝胶过滤以及有限蛋白酶解后的肽图谱分析，将源自培养基的SB - 1凝集素与种子SBA进行了比较；未发现这两种来源的凝集素之间存在差异。在N - 己酰 - 半乳糖胺 - 琼脂糖亲和柱上分级分离的大豆根提取物，用半乳糖洗脱后，得到了Mr为30,000和60,000的多肽。这些结果表明，大豆根中含有一种凝集素，其多肽组成与种子SBA和SB - 1凝集素的多肽组成相对应。
