Synthesis of two possible disulfide bonds containing peptide fragments (Cys6-Cys47, Cys48-Cys52 (Type I), and Cys6-Cys48, Cys47-Cys52 (Type II) of H-IGF-I) for the identification of disulfide bond linkage in recombinantly produced H-IGF-I

Article abstract of DOI:10.1246/bcsj.72.1827

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 fragments 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 of h-IGF-I(4-9,47-53), were chemically 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.