Expression Of A Gene For Human Insulin-like Growth Factor In E.coli And Bombyx Mori

A 588bp gene sequence (hIGF-I) of the whole cDNA of human insulin-like growth factor (hIGF-I) was synthesized. The sequence was cloned into pET-28a(+). The hIGF-I expression was performed in E.coli. SDS-PAGE and Western blotting suggests that the hIGF-I has the molecular weight of about 26kDa. The hIGF-I was cloned into pBacPAK8 to form pBacPAK8-hIGF-I plasmid. Recombinant virus Bm-Bac-hIGF-I was generated by cotransfection into BmN cells with the transfer plasmid pBacPAK8-hIGF-I and the modified Bombyx mori nuclear polyhedrosis virus Bm-BacPAK6 genomic DNA. SDS-PAGE shows that recombinant protein expressed in pupae are about 7.5 kDa and 22 kDa in molecular weight, and expression level of 4.51μg per milliliter hemolymph was detected by ELISA. These results show that the insect expression system has the ability to modify the protein from senior animal.. The protein expressed in Bombyx mori of 7.5 KDa is the same as the molecular weight of the mature hIGF-I. In the end of infection period, there is a band of 22 KDa in the SDS-PAGE which is equal to the theory. The speculation is the expression can not be modified thoroughly.