The Sequence Determinant Causing Different Folding Behaviors of Insulin and Insulin-like Growth Factor-1

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• 作者：Qi-Long Huang ; Jie Zhao ; Yue-Hua Tang ; Su-Qing Shao ; Gen-Jun Xu ; You-Min Feng
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：January 9, 2007
• 年：2007
• 卷：46
• 期：1
• 页码：218 - 224
• 全文大小：267K
• 年卷期：v.46,no.1(January 9, 2007)
• ISSN：1520-4995

文摘

Although insulin and insulin-like growth factor-1 (IGF-1) belong to the insulin superfamilyand share highly homologous sequences, similar tertiary structure, and a common ancestor molecule,amphioxus insulin-like peptide, they have different folding behaviors: IGF-1 folds into two thermodynamically stable tertiary structures (native and swap forms), while insulin folds into one unique stable structure.To further understand which part of the sequence determines their different folding behavior, based onprevious reports from the laboratory, two peptide models, [B9A][1-4]porcine insulin precursor (PIP)and [B10E][1-4]PIP, were constructed. The plasmids encoding the peptides were transformed into yeastcells for expression of the peptides; the results showed that the former peptide was expressed as singlecomponent, while the latter was expressed as a mixture of two components (isomer 1 and isomer 2). Theexpression results together with studies of circular dichoism, disulfide rearrangement, and refolding leadus to deduce that isomer 1 corresponds to the swap form and the isomer 2 corresponds to the native form.We further demonstrate that the sequence 1-4 plus B9 of IGF-1 B-domain can make PIP fold into twostructures, while sequence 1-5 of insulin B-chain can make IGF-1 fold into one unique structure. Inother words, it is the IGF-1 B-domain sequence that 1-4 allows IGF-1 folding into two thermodynamicallystable tertiary structures; this sequence plus its residue B9E can change PIP folding behavior from foldinginto one unique structure to two thermodynamically stable structures, like that of IGF-1.