The different folding behavior of insulin and insulin-like growth factor 1 is mainly controlled by their B-chain/domain.
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.
Guo
Zhan-Yun
ZY
State 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.
Shen
Lu
L
Feng
You-Min
YM
D000595:Amino Acid Sequence; D000818:Animals; D002021:Buffers; D004220:Disulfides / Q000737:chemistry; D005822:Genetic Vectors / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006868:Hydrolysis; D007328:Insulin / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011384:Proinsulin / Q000737:chemistry / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D011972:Receptor, Insulin / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D013816:Thermodynamics
D002021:Buffers; D004220:Disulfides; D007328:Insulin; D010446:Peptide Fragments; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D007334:Insulin-Like Growth Factor I; D011384:Proinsulin; D011972:Receptor, Insulin; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase