| A member of the Fibroblast Growth Factor family, Fibroblast Growth Factor-8, isoform a (FGF8a) is accepted as a crucial organizing signal during the development of vertebrate embryos. Furthermore, the FGF8a performs many other biological functions, such as healing tissue wound, culturing the neural stem cells and inducing it to dopaminergic neurons. So it is suggested that the potential application is huge for FGF8a to benefit the clinical treatment.In present study, it has proved that the soluble expression benefits to enhance final product yield and bioactivity of rhFGF8a protein comparing with the inclusion body expression. On the basis of inducing inclusion-body-expresstion bacterial strain, rhFGF8a-pET-22b(+)-Rosetta(DE3) to express soluble rhFGF8a, which had been built in former research, the optimum condition of soluble expression was obtained by having particularly studied several influencing factors of soluble expression such as induced temperature, concentration of IPTG, induced time, induced period and components of culture medium. The data suggested that the content of the soluble expressed rhFGF8a protein was optimized to more than 30% of the total bacterial proteins. Using the technique of chromatography, rhFGF8a protein was isolated and purified successfully. The result of SDS-PAGE (Sodium Dodecy Sulfate-Polyacrylamide Gel Electrophoresis) showed that the purity of rhFGF8a protein was above 90%. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-di-pheny- ltet-razolium bromide) assay revealed that the activity of the purified protein expressed solubly was higher than that in the form of inclusion body in Escherichia coli rhFGF8a-pET-22b(+)-Rosetta(DE3).In summary, the condition of soluble expression and the purification method of rhFGF8a protein, which have been established in this study, not only lay the foundation for the following research and large-scale industrial production but also could apply to the study of other similar members of Fibroblast Growth Factors.
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