Young N M, Oomen R P
Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada.
J Mol Biol. 1992 Dec 5;228(3):924-34. doi: 10.1016/0022-2836(92)90875-k.
Twelve plant lectins from the Papilionoideae subfamily were selected to represent a range of carbohydrate specificities, and their sequences were aligned. Two variability indices were applied to the aligned sequences and the results were analysed using the three-dimensional structures of concanavalin A and the pea lectin. The areas of greatest variability were located in the carbohydrate-binding site region, forming a perimeter around a well-conserved core. These residues are inferred to be specificity determining, in the manner of antibodies, and the most variable position corresponded to Tyr100 in concanavalin A, a known ligand contact residue. In addition to the five peptide loops known to form the binding site from crystallographic studies, a sixth segment with variable residues was located in the binding-site region, and this may contribute to oligosaccharide specificity. In their overall composition, the lectin sites resemble those of the sugar-transport proteins rather than antibodies. The prospects for modelling lectin binding sites by the methods used for antibodies were also assessed.
从蝶形花亚科中挑选出12种植物凝集素，以代表一系列碳水化合物特异性，并对它们的序列进行比对。将两个变异性指数应用于比对后的序列，并利用伴刀豆球蛋白A和豌豆凝集素的三维结构对结果进行分析。变异性最大的区域位于碳水化合物结合位点区域，围绕一个高度保守的核心形成一个周边区域。这些残基被推断以抗体的方式决定特异性，并且最可变的位置对应于伴刀豆球蛋白A中的Tyr100，这是一个已知的配体接触残基。除了从晶体学研究中已知的形成结合位点的五个肽环外，结合位点区域还存在一个具有可变残基的第六段，这可能有助于寡糖特异性。在其总体组成上，凝集素位点类似于糖转运蛋白的位点，而不是抗体的位点。还评估了用抗体所用方法对凝集素结合位点进行建模的前景。
