Zea mays L. transglutaminase expression in Escherichia coli

Background

Transglutaminase (protein-glutamine:amine γ-glutamyl-transferase, E.C. 2.3.2.13) catalyses acyl-transfer reactions between γ-carboxyamide groups of glutamine residues and the ε -amino group of lysines in proteins, leading to inter- or intramolecular cross-linking. Transglutaminases (TGs) have been found in mammals, plants, fish, nematodes and bacteria. Two maize cDNA clones (TGZ15 and TGZ21) that expressed active transglutaminase localized in chloroplasts were isolated [1, 2].

Results

A TGZ sequence was subcloned into pET (Novagen) vector (named as pET28a+TGZ4). The expression assays in E. coli BL21 DE3 cells showed that the main fraction of the protein (>80%) was found in the inclusion bodies (see Figure 1). The purification under denaturing conditions in FPLC system followed by a refolding step was a suitable procedure to obtain functional TGZ4p (see Figures 2,3). In addition, a specific antibody against TGZ4p was obtained in the laboratory for the immunolocalization of this protein in E. coli cells (see Figure 4).

Figure 1

Western blot of TGZ4p. S = soluble, IB = inslusion bodies

Figure 2

TGZ4p FPLC purification under denaturing conditions.

Figure 3

TGase activity of refolded TGZ4p against Tris and phosphate buffer.

Figure 4

TGZ4p TEM Immunolocalization, S=soluble, IB=inclusion body.

Conclusion

TGZ4p was expressed in E. coli mainly as inclusion bodies. The purification under denaturing conditions and refolding in vitro was a suitable procedure to obtain functional TG.