Pandolfino E R, Christie D J, Munske G R, Fry J, Magnuson J A
J Biol Chem. 1980 Sep 25;255(18):8772-5.
Binding of Cd2+ to concanavalin A and the subsequent induction of saccharide-binding activity has been studied at pH 6.5. We found that Cd2+ bound to both metal sites, S1 and S2, and that Cd2+ alone would induce sugar binding in concanavalin A. Using the fluorescent sugar 4-methylumbelliferyl alpha-D-mannopyranoside we determined that full saccharide-binding activity was obtained only when the total bound Cd2+ stoichiometry reached 2 ions/concanavalin A subunit. We also report evidence suggesting that the binding of Cd2+ to S2 is the crucial step in activation and that Cd2+ binding to S1 induces a form of concanavalin A similar to that induced by Zn2+, Ni2+, or Co2+ and different from that induced by Mn2+.
在pH 6.5条件下，研究了Cd2+与伴刀豆球蛋白A的结合以及随后糖结合活性的诱导情况。我们发现Cd2+与金属位点S1和S2都结合，并且单独的Cd2+会诱导伴刀豆球蛋白A中的糖结合。使用荧光糖4-甲基伞形基α-D-甘露吡喃糖苷，我们确定只有当总的结合Cd2+化学计量达到2个离子/伴刀豆球蛋白A亚基时，才能获得完全的糖结合活性。我们还报告了证据表明，Cd2+与S2的结合是激活的关键步骤，并且Cd2+与S1的结合诱导出一种类似于由Zn2+、Ni2+或Co2+诱导的伴刀豆球蛋白A形式，与由Mn2+诱导的不同。
