Lappi D A, Kapmeyer W, Beglau J M, Kaplan N O
Proc Natl Acad Sci U S A. 1978 Mar;75(3):1096-100. doi: 10.1073/pnas.75.3.1096.
Studies on the disulfide bond connecting the two polypeptide chains of ricin are reported. Reduction of this bond in the native protein requires approximately 50-fold more mercaptoethanol than the reduction of the bond in the protein denatured by sodium dodecyl sulfate. An improved procedure for the formation of this disulfide bond from recombined chains is reported. A and B chains spontaneously and rapidly reassociate into a stable complex with a sedimentation velocity similar to that of native oxidized ricin before the disulfide bond reforms. The mixture of both chains also behaves on Bio-Gel P-100 like native oxidized ricin. However, the complex formed by the two chains, assayed before the disulfide bond can reform, and reduced ricin, carboxymethylated to prevent reoxidation, shows a significant decrease in toxicity to mice and a decrease in ability to inhibit protein synthesis in HeLa cells in culture.
关于蓖麻毒素两条多肽链间二硫键的研究已有报道。与经十二烷基硫酸钠变性的蛋白质中的二硫键还原相比，天然蛋白质中该二硫键的还原需要约50倍量的巯基乙醇。本文报道了一种由重组链形成此二硫键的改进方法。在二硫键重新形成之前，A链和B链能自发且迅速地重新缔合成一种稳定的复合物，其沉降速度与天然氧化型蓖麻毒素相似。两条链的混合物在Bio-Gel P-100上的行为也与天然氧化型蓖麻毒素相同。然而，在二硫键能够重新形成之前进行检测的由两条链形成的复合物，以及经羧甲基化处理以防止再氧化的还原型蓖麻毒素，对小鼠的毒性显著降低，且在培养的HeLa细胞中抑制蛋白质合成的能力也有所下降。
