Expression and Receptor Binding Activity of Fusion Protein from Transforming Growth Factor- and GFP

A TGF-${\beta}1$/GFP monomeric fusion protein was cloned from pPK9A and pGFP-Cl plasmid by PCR amplification. The fusion protein was expressed in a $Bac-To-Bac^{TM}$ baculovirus expression system. A 45 kDa fusion protein was purified using an Ni-NTA column with 300 mM imidazol from a cell lysate infected with recombinant viruses for 72 h post-infection. The fusion protein cross-reacted with the commercial $TGF-{\beta}1$ polyclonal Ab as well as Ab raised against a precursor, monomeric $TGF-{\beta}1$, and GFP. The binding activity of the fusion protein with a $TGF-{\beta}1$ receptor was examined. Fluorescence was observed in Mv1Lu cells, yet not in insect cells treated with the fusion protein. No fluorescence was detected in Mv1Lu cells incubated with the fusion protein treated with Ab prior to the binding reaction, or with GFP alone, thereby indicating that the binding of the fusion protein was specific to $TGF-{\beta}1$ with a receptor.