Induction，denaturation and renaturation of Musa acuminata Bowman-Birk type protease inhibitor（ MaBBI1）

BBI（ Bowman-Birk protease inhibitor） is a kind of plant-derived protease inhibitor and rich in cysteine，it can inhibit serine proteases，including trypsase，chymase，elastase and so on. A Bowman-Birk type protease inhibitor gene（ MaBBI1） was cloned with the cDNA templates isolated and reversely transcribed from total RNA of banana（ Musa acuminata L. cv.Brazilian） roots and the primers were designed according to the sequence of wild Malaysian banana（ Musa acuminata subsp. Malaccensis） BBI gene（ GenBank: XM_009415512） published in NCBI. The full length of MaBBI1 gene with 381 bp encoding 126 amino acids including 12 cysteines （9.5%） was inserted into vector pGEX-6P-1 and transformed Escherichia coli Rossetta to induce the expression of recombinant proteins GST-MaBBI1. A lot of GST-MaBBI1 fusion proteins with predicted molecular mass of 40.8953 ku were induced by IPTG at 3 h. However，the GST-MaBBI1 fusion proteins were insoluble after IPTG induction and accumulating as inclusion bodies. To get the soluble GST-MaBBI1 fusion proteins，the inclusion bodies were denatured and renatured. The soluble fusion proteins GST-MaBBI1 laid the foundation for its further study in vitro.