Direct Identification of Disulfide Bond Linkages in Human Insulin-Like Growth Factor I (IGF-I) by Chemical Synthesis

Michio Iwai, Masakazu Kobayashi, Kouichl Tamura, Yoshinori Ishii, Hisashi Yamada, Mineo Niwa

The Journal of Biochemistry · 1989 · 30 citations · 0 references

Concepts

Abstract

The primary structure of human IGF-I, except for the disulfide bond system, has been reported by Rinderknecht and Humbel. IGF-I afforded the corresponding characteristic peptide fragment on V8 protease digestion, which contained Cys6, Cys47, Cys48, and Cys52. Two possible fragments, Type I with Cys6-Cys47 and Cys48-Cys52, and Type II with Cys6-Cys48 and Cys47-Cys52, were synthesized. The disulfide bond system of IGF-I was unequivocally determined to be the Type II form along with Cys18-Cys61. Interestingly, the Type I system was included in the disulfide bond isomer produced as the main by-product in the refolding step on IGF-I synthesis by the recombinant DNA method.