Nishihara T, Wyrick R E, Working P K, Chen Y H, Hedrick J L
Biochemistry. 1986 Oct 7;25(20):6013-20. doi: 10.1021/bi00368a027.
A cortical granule lectin was isolated from eggs of the South African clawed toad Xenopus laevis. The lectin was released from the cortical granules by activation of dejellied eggs with the Ca2+ ionophore A23187. The lectin was purified by affinity chromatography with its natural ligand, the egg jelly coat, chemically coupled to a Sepharose matrix. The purified lectin was homogeneous by the criteria of isoelectric focusing (pI = 4.6), immunodiffusion, and immunoelectrophoresis but existed in two different molecular weight isomers as determined by sedimentation velocity ultracentrifugation and disc gel electrophoresis. Molecular weights of the isomers were determined by ultracentrifugation, disc gel electrophoresis, and gel filtration and found to be 539,000 and 655,000. Chemically, the lectin was a metalloglycoprotein, composed of 84.0% protein, 15.8% carbohydrate, and 0.19% calcium. No unusual types or amounts of amino acids were present. The carbohydrate moiety was composed of fucose, mannose, galactose, glucosamine, galactosamine, and sialic acid. The monosaccharide specificity of the lectin was investigated with the sugar inhibition of the precipitin reaction in gels. The lectin was specific for D-galactosyl sugars with the configuration at carbon atoms 2-4 of primary importance.
从南非爪蟾非洲爪蟾的卵中分离出一种皮质颗粒凝集素。通过用钙离子载体A23187激活去胶膜的卵，使凝集素从皮质颗粒中释放出来。利用其天然配体——卵胶膜，将其化学偶联到琼脂糖基质上，通过亲和层析对凝集素进行纯化。通过等电聚焦（pI = 4.6）、免疫扩散和免疫电泳标准，纯化后的凝集素是均一的，但通过沉降速度超速离心和圆盘凝胶电泳测定，它以两种不同分子量的异构体形式存在。通过超速离心、圆盘凝胶电泳和凝胶过滤测定异构体的分子量，发现分别为539,000和655,000。从化学组成来看，该凝集素是一种金属糖蛋白，由84.0%的蛋白质、15.8%的碳水化合物和0.19%的钙组成。不存在异常类型或数量的氨基酸。碳水化合物部分由岩藻糖、甘露糖、半乳糖、葡糖胺、半乳糖胺和唾液酸组成。利用凝胶中沉淀素反应的糖抑制法研究了该凝集素的单糖特异性。该凝集素对D-半乳糖基糖具有特异性，其中碳原子2-4处的构型最为重要。
