A polypeptide selected from the group consisting of: (1) a polypeptide having the amino acid sequence of SEQ ID NO: 1, and (2) a polypeptide having an amino acid sequence in which the third amino acid of the amino acid sequence of SEQ ID NO: 1 is substituted by another amino acid and having insulin-like growth factor 1 (IGF-1) activity； a DNA encoding said polypeptide； a vector containing said DNA； a host cell containing said vector； and a method for preparing a recombinant protein using said polypeptide.本發明係關於使用選自(1)具有序列號碼1所記載之胺基酸序列之多肽，及(2)具有於序列號碼1所記載之胺基酸序列中，第3個胺基酸為其他胺基酸所取代之胺基酸序列，而且具有類胰島素成長因子1(IGF－1)活性之多肽所成群之多肽；編碼上述多肽之DNA；含有上述DNA之載體(vector)；含有上述載體之宿主細胞，以及使用上述多肽之製造基因重組蛋白質之方法。
