title: Expression and purification of large active GST fusion enzymes.
abstract: GST fusion proteins expressed in bacteria often tend to form aggregates and are inefficiently purified by standard procedures, which employ a mixture of detergents that compromise the binding efficiency to the affinity resin and the biological activity of the recombinant proteins. Moreover, the binding to the resin is negatively affected by the molecular weight of the fusion protein. Here we report a simple and efficient method to purify active large GST-tagged proteins, which uses high ionic strength buffer to solubilize the protein aggregates in a bacterial lysate. Affinity-chromatography purification is achieved by adopting two columns connected in series, which facilitate the binding of large GST fused molecules. This approach was applied to purify the 180-kDa GST-tagged mitochondrial RNA polymerase. We also report conditions for simple and efficient GST tag removal from the eluted protein. Finally we demonstrate that the recombinant enzyme is capable to catalyze RNA synthesis.
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Deceglie
authors.forename: Claudia
authors.initials: C
authors.lastname: Lionetti
authors.forename: Marina
authors.initials: M
authors.lastname: Roberti
authors.forename: Palmiro
authors.initials: P
authors.lastname: Cantatore
authors.forename: Paola Loguercio
authors.initials: PL
authors.lastname: Polosa
mesh_terms: D002846:Chromatography, Affinity; D005982:Glutathione Transferase / Q000302:isolation & purification / Q000378:metabolism*; D009994:Osmolar Concentration; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase