Fully oxidized scrambled isomers are essential and predominant folding intermediates of cardiotoxin-III
- 作者：Jui-Yoa Chang ; Bao-Yuan Lu ; Curtis C.-J. Lin and Chin Yu
- 关键词：CTX-III ; Cardiotoxin III ; Protein oxidative folding ; Folding intermediate ; Scrambled isomer of CTX-III
- 刊名：FEBS Letters
- 出版年：2006
- 期刊代码：70_00145793
- 类别：bio
- 出版时间：23 January 2006
- 卷：580
- 期：2
- 页码：656-660
- 文件大小：189 K
摘要
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.