Document Detail

The CXC motif: a functional mimic of protein disulfide isomerase.
MedLine Citation:
PMID:  12731880     Owner:  NLM     Status:  MEDLINE    
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.
Kenneth J Woycechowsky; Ronald T Raines
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biochemistry     Volume:  42     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  2003 May 
Date Detail:
Created Date:  2003-05-06     Completed Date:  2003-06-24     Revised Date:  2013-06-09    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  5387-94     Citation Subset:  IM    
Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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MeSH Terms
Amino Acid Motifs
Binding Sites
Cysteine / chemistry
Disulfides / chemistry,  metabolism
Escherichia coli / enzymology*,  metabolism*
Genetic Vectors
Molecular Mimicry*
NADP / metabolism
Protein Conformation
Protein Disulfide-Isomerases / chemistry,  metabolism*
Protein Folding
Spectrometry, Fluorescence
Substrate Specificity
Sulfhydryl Compounds / chemistry,  metabolism
Thioredoxin-Disulfide Reductase / metabolism
Thioredoxins / genetics,  metabolism*
Grant Support
Reg. No./Substance:
0/Disulfides; 0/Sulfhydryl Compounds; 52-90-4/Cysteine; 52500-60-4/Thioredoxins; 53-59-8/NADP; EC Reductase; EC Disulfide-Isomerases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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