A polypeptide selected from the group consisting of (1) a polypeptide havingthe amino acid sequence represented by SEQ ID NO:1 and (2) a polypeptidehaving an amino acid sequence derived from the amino acid sequence representedby SEQ ID NO:1 by substitution of the amino acid at the 3-position by anotheramino acid and having an insulin-like growth factor 1 (IGF-1) activity; a DNAencoding the above polypeptide; a vector containing the above DNA; a host cellcontaining the above vector; and a method of producing a recombinant proteinby using the above polypeptide.