The CXC motif: a functional mimic of protein disulfide isomerase.
The CXC motif: a functional mimic of protein disulfide isomerase.
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DOI：
10.1021/bi026993q
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发表时间：
2003-05
期刊：
影响因子：
2.9
通讯作者：
K. J. Woycechowsky;R. Raines
中科院分区：
文献类型：
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作者：
K. J. Woycechowsky;R. Raines
蛋白质二硫键异构酶（PDI）利用活性位点序列Cys-Gly-His-Cys（CGHC; E度= -180 mV）在氧化蛋白质折叠期间实现硫醇-二硫键交换。在此，Cys-Gly-Cys-NH（2）（CGC）肽显示出具有接近于PDI的二硫键还原电位（E度=-167mV）。该肽具有低于谷胱甘肽的硫醇酸解离常数（pK（a）= 8.7）。这些属性赋予CGC肽大量的二硫键异构化活性。大肠杆菌硫氧还蛋白（Trx）利用活性位点序列Cys-Gly-Pro-Cys（CGPC; E度= -270 mV）来实现二硫键还原。从Trx活性位点去除脯氨酸残基产生具有极大不稳定的二硫键的CGC活性位点（E度>或= -200 mV）。DeltaP 34变体保持高构象稳定性，并且仍然是硫氧还蛋白还原酶的底物。与野生型酶的还原形式相反，DeltaP 34 Trx的还原形式具有二硫键异构化活性，其比CGC肽的活性高25倍。因此，活性位点残基的合理缺失可以赋予酶新的和期望的功能。此外，肽和蛋白质中的CXC基序提供了PDI的功能模拟。
Protein disulfide isomerase (PDI) utilizes the active site sequence Cys-Gly-His-Cys (CGHC; E degrees ' = -180 mV) to effect thiol-disulfide interchange during oxidative protein folding. Here, the Cys-Gly-Cys-NH(2) (CGC) peptide is shown to have a disulfide reduction potential (E degrees ' = -167 mV) that is close to that of PDI. This peptide has a thiol acid dissociation constant (pK(a) = 8.7) that is lower than that of glutathione. These attributes endow the CGC peptide with substantial disulfide isomerization activity. Escherichia coli thioredoxin (Trx) utilizes the active site sequence Cys-Gly-Pro-Cys (CGPC; E degrees ' = -270 mV) to effect disulfide reduction. Removal of the proline residue from the Trx active site yields a CGC active site with a greatly destabilized disulfide bond (E degrees ' >or= -200 mV). The DeltaP34 variant retains high conformational stability and remains a substrate for thioredoxin reductase. In contrast to the reduced form of the wild-type enzyme, the reduced form of DeltaP34 Trx has disulfide isomerization activity, which is 25-fold greater than that of the CGC peptide. Thus, the rational deletion of an active site residue can bestow a new and desirable function upon an enzyme. Moreover, a CXC motif, in both a peptide and a protein, provides functional mimicry of PDI.