A Simple Method to Produce Recombinant Mammalian Serum Albumins in Escherichia coli Preserving Intact Antigenic Properties.

Serum albumin (SA) plays a fundamental role in the transport of metabolites and endogenous ligands. Additionally, animal albumins are potent allergens. Heterologous expression of SAs is challenging due to their complex structure. In this study, we describe a simple method for enhanced production of soluble and functional recombinant feline (rFel d 2) and canine (rCan f 3) albumins in the standard E. coli strain BL21 (DE3). To achieve this, the 18-amino acid signal peptide was removed from the N-terminus of each albumin. To improve expression, folding, and solubility of recombinant proteins, we tested an extended panel of fusion proteins. Among them, MBP (maltose-binding protein), TF (trigger factor), and NusA (E. coli transcription termination factor) allowed the production of soluble fusion forms of rFel d 2 and rCan f 3. To confirm the structural integrity of the products, we analyzed the IgE-binding characteristics of recombinant versus native albumins. rFel d 2 and rCan f 3 fused with TF, MBP, and NusA bound albumin-specific immunoglobulin E (in 26/33, 29/33, 31/33, and 27/29, 26/29, 27/29 cases, respectively, comparable to native Fel d 2 and Can f 3. Thus, removal of the signal peptide combined with fusion partners enables expression of Fel d 2 and Can f 3 in E. coli with preserved antigenic properties.