PMID:12731880
| Citation |
Woycechowsky, KJ and Raines, RT (2003) The CXC motif: a functional mimic of protein disulfide isomerase. Biochemistry 42:5387-94 |
|---|---|
| Abstract |
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. |
| Links |
PubMed PMC2819094 Online version:10.1021/bi026993q |
| Keywords |
Amino Acid Motifs; Binding Sites; Cysteine/chemistry; Disulfides/chemistry; Disulfides/metabolism; Escherichia coli/enzymology; Escherichia coli/metabolism; Genetic Vectors; Kinetics; Molecular Mimicry; Mutation; NADP/metabolism; Oxidation-Reduction; Protein Conformation; Protein Disulfide-Isomerases/chemistry; Protein Disulfide-Isomerases/metabolism; Protein Folding; Spectrometry, Fluorescence; Substrate Specificity; Sulfhydryl Compounds/chemistry; Sulfhydryl Compounds/metabolism; Thioredoxin-Disulfide Reductase/metabolism; Thioredoxins/genetics; Thioredoxins/metabolism |
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