Hemperly J J, Hopp T P, Becker J W, Cunningham B A
J Biol Chem. 1979 Jul 25;254(14):6803-10.
We have determined the subunit structure of the glucose- and mannose-binding lectin favin, from Vicia faba. The molecule is composed of two nonidentical polypeptide chains held together by noncovalent interactions. We have determined the complete amino acid sequence of the smaller alpha chain (Mr = 5,571) and shown that it is homologous to the alpha chain of the lectins from lentil and pea and to residues 72 to 120 of concanavalin A (Con A). The larger beta chain (Mr = 20,000) contains carbohydrate and is homologous to the beta chain of lentil, pea, soybean, peanut, and red kidney bean lectins and is homologous to a portion of the Con A molecule beginning at residue 122. Favin also contains a minor component, beta' (Mr = 18,700), that closely resembles the beta chain but lacks carbohydrate and may, on the basis of apparent molecular weight, lack some part of the COOH-terminal region of the polypeptide chain. Although favin is similar to Con A, it, like the lentil and pea lectins, appears to lack residues corresponding to positions 1 to 71 of Con A. Because these residues contribute significantly to the carbohydrate binding site of Con A, the lack of this region in the otherwise homologous lectin favin suggests that the carbohydrate binding site of favin differs from that of Con A or that the region represented by residues 1 to 71 of Con A is located in a different portion (i.e. in the beta chain) of the favin molecule.
我们已经确定了来自蚕豆的葡萄糖和甘露糖结合凝集素蚕豆凝集素的亚基结构。该分子由两条不同的多肽链通过非共价相互作用结合在一起组成。我们已经确定了较小的α链（Mr = 5571）的完整氨基酸序列，并表明它与小扁豆和豌豆凝集素的α链以及伴刀豆球蛋白A（Con A）的72至120位残基同源。较大的β链（Mr = 20000）含有碳水化合物，与小扁豆、豌豆、大豆、花生和红芸豆凝集素的β链同源，并且与Con A分子从122位残基开始的一部分同源。蚕豆凝集素还含有一种次要成分β'（Mr = 18700），它与β链非常相似，但不含碳水化合物，并且根据表观分子量，可能缺少多肽链COOH末端区域的某些部分。尽管蚕豆凝集素与Con A相似，但它与小扁豆和豌豆凝集素一样，似乎缺少与Con A的1至71位相对应的残基。由于这些残基对Con A的碳水化合物结合位点有重要贡献，在其他方面同源的凝集素蚕豆凝集素中缺少该区域表明蚕豆凝集素的碳水化合物结合位点与Con A不同，或者Con A的1至71位残基所代表的区域位于蚕豆凝集素分子的不同部分（即β链）中。
