Expression of Bm-TFF2 mutants in Escherichia coli andtheir cell migration-promoting activity

Bm-TFF2, a trefoil factor from the large-webbed bell toad (Bombina maxima), can stimulate cell migration and inhibit cell apoptosis. To study the structure-function relationship of Bm-TFF2, we constructed wild-type and mutated Bm-TFF2 plasmids and expressed recombinant proteins in E. coli. The wild-type Bm-TFF2 gene encoding mature peptide was obtained by RT-PCR, while the N-terminal, C-terminal and two arginine mutated Bm-TFF2 clones were constructed, and ligated into pET-32a(+) expression vectors. The fusion proteins were induced by IPTG at 37°C. The mutant Bm-TFF2 fusion proteins expressed mainly in the inclusion bodies. The mutant (TRX)/Bm-TFF2 could be purified by using Ni2+-chelating chromatography and reverse-phase HPLC from the inclusion body supernatant. The fusion proteins were analyzed by SDS-PAGE and Western blotting. The yield of mutant Bm-TFF2 fusion proteins of above 95% purity was about 20 mg/L. All three recombinant mutant proteins can promote the migration of AGS cells in a dose-dependent manner with no obvious activity difference.