Expression, purification and structural analysis of csgF gene of curli systems from Escherichia coli CFT073

Abstract:

[Objective] In this experiment we explored the expression, purification condition and tertiary structure of the Curli family protein CsgF of Escherichia coli CFT073, to provide a theoretical basis for studying the biosynthetic mechanism of Curli. [Methods] The csgF gene was amplified by PCR from E. coli CFT073 genomic DNA, and the recombinant plasmids such as pET28a-csgF(nsp)-N-6His, pET28a-csgF(20?129)-N-6His, pET28a-csgF-C-6His, and pET28a-csgF(nsp)-C-6His, were constructed. These were then transformed into E. coli strain DH5α, and the expression of the csgF gene in E. coli BL21(DE3) was induced by isopropyl β-D-1-Thiogalactopyranoside (IPTG). Next, CsgF was separated and purified by Ni-chelating affinity chromatograph and gel exclusion chromatography, and was determined by SDS-PAGE and Western blotting assay. The protein interaction of CsgF and CsgG was studied by pull down experiments. The tertiary structure of CsgF was constructed based on homology modeling. [Results] The purified CsgF protein of high stability was obtained in condition of 50 mmol/L sodium acetate (pH 5.0), 150 mmol/L NaCl and 5% glycerol. Pull down experiments showed there was interaction between CsgF and CsgG. Homology modeling demonstrated that the tertiary structure of CsgF was of (β/α) model. [Conclusion] Our findings can lay a foundation for studying the structure and function of CsgF.

Key words:Escherichia coli CFT073, CsgF, Gene cloning, Protein expression and purification, Gel exclusion chromatography