Wycoff K L, van Rhijn P, Hirsch A M
Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles 90095-1606, USA.
Plant Mol Biol. 1997 May;34(2):295-306. doi: 10.1023/a:1005817114562.
Soybean (Glycine max L. Merr.) mutants lacking the ability to produce the lectin normally found in soybean seeds (SBL) are designated Le-. A protein of higher molecular weight that cross-reacts with antibodies raised to SBL was found at nearly equivalent levels in roots, hypocotyls, and leaves, and at lower levels in cotyledons and dry seeds of both Le+ and Le- soybean cultivars. Earlier work suggested that this protein was a novel lectin. Clones isolated from a Le- soybean root cDNA library produced a cross-reacting protein of the same size in Escherichia coli. Sequence analysis of these clones revealed a high degree of similarity to the ribosomal protein P0. The cross-reacting protein co-purified with ribosomes, and a monoclonal antibody raised to purified brine shrimp P0 cross-reacted to the same protein. The protein showed no lectin activity in a hemagglutination assay, nor did it bind to an N-acetyl-D-galactosamine affinity column. On the basis of this evidence, we conclude that the SBL-cross-reacting protein is not a lectin but a homologue of the ribosomal protein P0. Consequently, Le- soybeans must produce a lectin that is dissimilar to SBL at both the DNA and amino acid levels and we suggest that it is this lectin which is involved in nodulation.
缺乏产生通常存在于大豆种子中的凝集素（SBL）能力的大豆（Glycine max L. Merr.）突变体被命名为Le-。在Le+和Le-大豆品种的根、下胚轴和叶片中，发现了一种与针对SBL产生的抗体发生交叉反应的高分子量蛋白质，其含量几乎相同，而在子叶和干种子中的含量较低。早期的研究表明这种蛋白质是一种新型凝集素。从Le-大豆根cDNA文库中分离出的克隆在大肠杆菌中产生了相同大小的交叉反应蛋白。对这些克隆的序列分析显示与核糖体蛋白P0有高度相似性。交叉反应蛋白与核糖体共纯化，并且针对纯化的卤虫P0产生的单克隆抗体与同一蛋白发生交叉反应。在血细胞凝集试验中，该蛋白没有凝集素活性，也不与N-乙酰-D-半乳糖胺亲和柱结合。基于这些证据，我们得出结论，与SBL交叉反应的蛋白不是凝集素，而是核糖体蛋白P0的同源物。因此，Le-大豆必须产生一种在DNA和氨基酸水平上都与SBL不同的凝集素，我们认为正是这种凝集素参与了根瘤形成。
