SMALL MOLECULE CATALYST OF PROTEIN FOLDING

蛋白质二硫键异构酶（PDI）催化的蛋白质二硫键异构酶（ 底物蛋白中的二硫键。 两个半胱氨酸-甘氨酸-组氨酸-半胱氨酸活性 位点提供低pKa的硫醇和高pKa的二硫键。 还原电位（E？？） 反式-1，20双（2-巯基乙酰氨基）环己烷（BMC）模拟PKa， E？？的PDI活性位点。 体外试验表明，BMC是 一种能有效催化乱序核糖核酸酶再活化的催化剂 （RNase）A，具有非天然二硫键的底物。 体内 试验表明，酵母细胞生长培养基中的BMC增加了 分泌天然酸性磷酸酶，其具有八个二硫键。 其效果类似于在生长期内PDI的过度产生。 酵母细胞 BMC的单硫醇类似物，N-甲基-巯基乙酰胺 (NMA)，也催化乱序RNA酶A的再活化，但较少 比BMC更有效。 这些数据表明， 低巯基pKa和高二硫化物E？有效催化 蛋白质中天然二硫键的形成。 此外，BMC是一个 用于蛋白质的体外和体内折叠的有用催化剂， 含有多个二硫键。

Protein disulfide isomerase (PDI) catalyzed the interchange of disulfide bonds in substrate proteins. The two Cys-Gly-His-Cys active sites provide a thiol of low pKa and a disulfide bond of high reduction potential (E??). Trans-1,20bis(2-mercaptoacetamido)cyclohexane (BMC) mimics the pKa and E?? of the PDI active sites. In vitro assays demonstrate that BMC is an efficient catalyst of the reactivation of scrambled ribonuclease (Rnase) A, a substrate with non-native disulfide bonds. In vivo assays show that BMC in the growth medium of yeast cells increases the secretion of native acid phosphatase, which has eight disulfide bonds. The effect is similar to that from the overproduction of PDI in the yeast cells. A monothiol analog of BMC, N-methyl-mercaptoacetamide (NMA), also catalyzes the reactivation of scrambled Rnase A, but less efficiently than does BMC. These data indicate that molecules with a low thiol pKa and high disulfide E?? catalyze effectively the formation of native disulfide bonds in proteins. Moreover, BMC is a useful catalyst for the in vitro and in vivo folding of proteins that contain multiple disulfide bonds.