Fujita-Yamaguchi Y, Oishi K, Suzuki K, Imahori K
Biochim Biophys Acta. 1982 Feb 4;701(1):86-92. doi: 10.1016/0167-4838(82)90315-6.
The anti-B specific lectin produced by Streptomyces sp. was shown to have two carbohydrate-binding sites with binding constants of 8.3 . 10(3) M-1 (15 degrees C) and 2.2 . 10(3) M-1 (4 degrees C) for L-rhamnose and D-galactose, respectively, calculated according to Scatchard plots. The binding of specific sugars to the lectin not only induced a peculiar ultraviolet difference spectrum showing a blue shift of tryptophan absorption, but also caused crystallization of the lectin at a concentration of 1 mg per ml or more. The solvent-perturbation studies on the lectin showed that the number of solvent-exposed tryptophan (or average extent of exposure) was two in the absence of L-rhamnose, and three in the presence of the sugar. This suggests that one tryptophan residue appears outside as the result of sugar-binding to the lectin, which is reflected by the difference spectra. Oxidation of two tryptophan residues with N-bromosuccinimide led to complete loss of carbohydrate-binding activity of the lectin, indicating that these residues are important for retaining the activity.
链霉菌属产生的抗B特异性凝集素显示有两个碳水化合物结合位点，根据Scatchard图计算，其对L-鼠李糖和D-半乳糖的结合常数分别为8.3×10³ M⁻¹（15℃）和2.2×10³ M⁻¹（4℃）。特定糖类与凝集素的结合不仅诱导出一种特殊的紫外差异光谱，显示色氨酸吸收出现蓝移，而且在浓度为每毫升1毫克或更高时会导致凝集素结晶。对该凝集素的溶剂扰动研究表明，在不存在L-鼠李糖时，溶剂暴露的色氨酸数量（或平均暴露程度）为两个，而在有糖存在时为三个。这表明由于糖类与凝集素结合，一个色氨酸残基出现在外部，这在差异光谱中得到反映。用N-溴代琥珀酰亚胺氧化两个色氨酸残基导致凝集素的碳水化合物结合活性完全丧失，表明这些残基对于保持活性很重要。
