Abstract
Scrambled isomers (X-isomers) are fully oxidized, non-native isomers of disulfide proteins. They have been shown to represent important intermediates along the pathway of oxidative folding of numerous disulfide proteins. A simple method to assess whether X-isomers present as folding intermediate is to conduct oxidative folding of fully reduced protein in the alkaline buffer alone without any supplementing thiol catalyst or redox agent. Cardiotoxin-III (CTX-III) contains 60 amino acids and four disulfide bonds. The mechanism of oxidative folding of CTX-III has been systematically characterized here by analysis of the acid trapped folding intermediates. Folding of CTX-III was shown to proceed sequentially through 1-disulfide, 2-disulfide, 3-disulfide and 4-disulfide (scrambled) isomers as folding intermediates to reach the native structure. When folding of CTX-III was performed in the buffer alone, more than 97% of the protein was trapped as 4-disulfide X-isomers, unable to convert to the native structure due to the absence of thiol catalyst. In the presence of thiol catalyst (GSH) or redox agents (GSH/GSSG), the recovery of native CTX-III was 80-85%. These results demonstrate that X-isomers play an essential and predominant role in the oxidative folding of CTX-III.
Original language | English (US) |
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Pages (from-to) | 656-660 |
Number of pages | 5 |
Journal | FEBS Letters |
Volume | 580 |
Issue number | 2 |
DOIs | |
State | Published - Jan 23 2006 |
Keywords
- CTX-III
- Cardiotoxin III
- Folding intermediate
- Protein oxidative folding
- Scrambled isomer of CTX-III
ASJC Scopus subject areas
- Biophysics
- Structural Biology
- Biochemistry
- Molecular Biology
- Genetics
- Cell Biology