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Updated: Jun 5, 2026

A Guide to Production, Crystallization, and Structure Determination of Human IKK1/α
Published on: November 2, 2018
The different folding behavior of insulin and insulin-like growth factor 1 is mainly controlled by their
Zhan-Yun Guo1, Lu Shen, You-Min Feng
1State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China.
Abstract:
Although insulin and insulin-like growth factor 1 (IGF-1) share homologous sequence, similar tertiary structure, weakly overlapped biological activity, and a common ancestor, the two highly homologous sequences encode different folding behavior: insulin folds into one unique stable tertiary structure while IGF-1 folds into two disulfide isomers with similar thermodynamic stability. To further elucidate the molecular mechanism of their different folding behavior, we prepared two single-chain hybrids of insulin and IGF-1, Ins(A)/IGF-1(B) and Ins(B)/IGF-1(A), as well as a mini-IGF-1 by means of protein engineering and studied their structure as well as folding behavior. Both mini-IGF-1 and Ins(A)/IGF-1(B) fold into two thermodynamically stable disulfide isomers in vivo and in vitro just like that of IGF-1, while Ins(B)/IGF-1(A) folds into one unique thermodynamically stable tertiary structure in vivo and in vitro just like that of insulin. So we deduce that the different folding behavior of insulin and IGF-1 is mainly controlled by their B-chain/domain. By V8 endoproteinase digestion and circular dichroism analysis, as well as insulin receptor binding assay, we deduce that Ins(B)/IGF-1(A), isomer 2 of mini-IGF-1, and isomer 2 of Ins(A)/IGF-1(B) adopt native IGF-1/insulin-like three-dimensional structure with native disulfides, while isomer 1 of mini-IGF-1 and isomer 1 of Ins(A)/IGF-1(B) adopt the swap IGF-1-like three-dimensional structure with swap disulfides.
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