Zapun A, Missiakas D, Raina S, Creighton T E
European Molecular Biology Laboratory, Heidelberg, Germany.
Biochemistry. 1995 Apr 18;34(15):5075-89. doi: 10.1021/bi00015a019.
DsbC is a soluble protein of the bacterial periplasm that was identified genetically as being involved in protein disulfide formation. The gene sequence was corrected to include an additional proline residue and was then consistent with the molecular weight of the purified protein. Gel filtration and subunit hybridization indicate that DsbC is a stable dimer of identical subunits. Each subunit has a -Cys-Gly-Tyr-Cys- segment that forms an unstable and reactive disulfide bond; only the first cysteine residue is accessible, similar to thioredoxin and DsbA. The other two cysteine residues of DsbC form a buried, structural disulfide bond. The reactivities and stabilities of the active site disulfide bond of DsbC have been characterized and compared to that of DsbA. Both are very unstable and can be transferred rapidly to reduced proteins and peptides, although they differ somewhat in their kinetic reactivities. The two active sites of the DsbC dimer appear to function independently. DsbC is much more active than DsbA in catalyzing protein disulfide rearrangements, and this may be its main function in vivo.
DsbC是细菌周质中的一种可溶性蛋白，通过遗传学方法鉴定其参与蛋白质二硫键的形成。对该基因序列进行了校正，使其包含一个额外的脯氨酸残基，随后与纯化蛋白的分子量相符。凝胶过滤和亚基杂交表明，DsbC是由相同亚基组成的稳定二聚体。每个亚基都有一个-Cys-Gly-Tyr-Cys-片段，该片段形成一个不稳定且具有反应性的二硫键；只有第一个半胱氨酸残基是可及的，这与硫氧还蛋白和DsbA相似。DsbC的另外两个半胱氨酸残基形成一个埋藏的、起结构作用的二硫键。已对DsbC活性位点二硫键的反应性和稳定性进行了表征，并与DsbA的进行了比较。两者都非常不稳定，并且可以迅速转移到还原的蛋白质和肽上，尽管它们在动力学反应性上略有不同。DsbC二聚体的两个活性位点似乎独立发挥作用。在催化蛋白质二硫键重排方面，DsbC比DsbA活性高得多，这可能是其在体内的主要功能。
