Cooper D N, Barondes S H
J Biol Chem. 1981 May 25;256(10):5046-51.
Purpurin, the lectin from Dictyostelium purpureum, has been resolved into seven tetrameric isolectins by polyacrylamide gel electrophoresis at pH 8.9. The isolectins are assembled from four distinct subunits resolved by electrophoresis in sodium dodecyl sulfate and by tryptic peptide mapping. Two of the subunits combine randomly with each other to form mixed tetramers (I4, I3II1, I2II2, I1II3, II4) in binomial proportions. The other two subunits (III and IV) form only homotetramers. The isolectins can be functionally discriminated and separated on the basis of their relative affinities for columns derivatized with complementary saccharides. On the basis of relative sensitivity to hapten inhibitors of hemagglutination, isolectins III4 and IV4 are distinct from each other and from isolectins composed of subunits I and II. However, isolectins of I and II are not distinguishable on the basis of hemagglutination inhibition. None of the subunits are glycosylated, and all form tetramers with molecular weights of approximately 88,000. The existence of multiple functionally distinct forms suggests that lectin function in cellular slime molds may be more complex than presently envisioned.
紫红素，来自紫盘基网柄菌的凝集素，在pH 8.9条件下通过聚丙烯酰胺凝胶电泳已被解析为七种四聚体同工凝集素。这些同工凝集素由通过十二烷基硫酸钠电泳和胰蛋白酶肽图谱解析出的四个不同亚基组装而成。其中两个亚基彼此随机组合形成二项式比例的混合四聚体（I4、I3II1、I2II2、I1II3、II4）。另外两个亚基（III和IV）仅形成同型四聚体。这些同工凝集素可根据它们对用互补糖类衍生化的柱的相对亲和力进行功能区分和分离。基于对血凝素凝集作用的半抗原抑制剂的相对敏感性，同工凝集素III4和IV4彼此不同，也与由亚基I和II组成的同工凝集素不同。然而，基于血凝抑制作用，I和II的同工凝集素无法区分。所有亚基均未糖基化，且都形成分子量约为88,000的四聚体。多种功能不同形式的存在表明，细胞黏菌中的凝集素功能可能比目前所设想的更为复杂。
