Foriers A, Lebrun E, Van Rapenbusch R, de Neve R, Strosberg A D
J Biol Chem. 1981 Jun 10;256(11):5550-60.
The subunit structure and complete amino acid sequence of the lectin extracted from Lens culinaris (LcL) seeds was determined. In previous studies, the primary structure of the alpha-chain (Mr = 5,710) was shown to be homologous to the alpha-chain of the lectin from Pisum sativum, the Vicia cracca glucose-specific lectin, and a region in the middle of the concanavalin A sequence (residues 70-121). The complete amino acid sequence of the beta-chain (Mr = 17,572) has been determined from 11 tryptic peptides, 4 peptides derived by chemical cleavage of the beta-chain at its three tryptophan residues, 11 peptides obtained after digestion with Staphylococcus aureus protease, and 5 tryptic peptides from the succinylated polypeptide chain. The extensive homologies by alignment of the alpha- and beta-chains of the L. culinaris lectin with portions of concanavalin A situated between 1 to 45 and 70 to 237, suggest that the L. culinaris and Canavalia ensiformis lectins have evolved from each other. A comparison was made between the secondary structure of the C. ensiformis lectin and the probable secondary structure of the L. culinaris lectin as predicted by two different methods. The results indicate that the folding of these two polypeptides has been particularly well conserved during evolution. It is suggested that the L. culinaris lectin is synthesized as a single polypeptide chain and cleaved subsequently into two or possibly three fragments, two of which would be alpha and beta and the third a fragment homologous to portion 46 to 69 in concanavalin A. As in favin, the amino acids postulated to be involved in the formation of the hydrophobic cavity and the sugar and metal binding sites are highly conserved in L. culinaris lectin.
测定了从兵豆（LcL）种子中提取的凝集素的亚基结构和完整氨基酸序列。在先前的研究中，α链（Mr = 5,710）的一级结构显示与豌豆凝集素的α链、广布野豌豆葡萄糖特异性凝集素以及伴刀豆球蛋白A序列中间区域（第70 - 121位残基）同源。β链（Mr = 17,572）的完整氨基酸序列已从11个胰蛋白酶肽段、通过在β链的三个色氨酸残基处进行化学裂解得到的4个肽段、用金黄色葡萄球菌蛋白酶消化后得到的11个肽段以及琥珀酰化多肽链的5个胰蛋白酶肽段中确定。通过将兵豆凝集素的α链和β链与伴刀豆球蛋白A位于1至45和70至237之间的部分进行比对，发现广泛的同源性，这表明兵豆凝集素和刀豆凝集素是相互演化而来的。对刀豆凝集素的二级结构与通过两种不同方法预测的兵豆凝集素可能的二级结构进行了比较。结果表明，这两种多肽的折叠在进化过程中得到了特别好的保留。有人提出，兵豆凝集素最初作为一条单一的多肽链合成，随后裂解为两个或可能三个片段，其中两个是α链和β链，第三个片段与伴刀豆球蛋白A中第46至69位的部分同源。与蚕豆凝集素一样，推测参与疏水腔形成以及糖和金属结合位点形成的氨基酸在兵豆凝集素中高度保守。
