Expression and purification of the mitochondrial serine protease LACTB as an N-terminal GST fusion protein in Escherichia coli

• Published in: Protein expression and purification 2006-02, Vol.45 (2), p.335-342
• Main Authors: Liobikas, Julius, Polianskyte, Zydrune, Speer, Oliver, Thompson, James, Alakoskela, Juha-Matti, Peitsaro, Nina, Franck, Marina, Whitehead, Maria A., Kinnunen, Paavo J.K., Eriksson, Ove
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; beta-Lactamases - genetics; beta-Lactamases - metabolism; d-Transpeptidase; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Humans; LACTB; Membrane Proteins - genetics; Membrane Proteins - isolation & purification; Membrane Proteins - metabolism; Mice; Mitochondria; Mitochondria - enzymology; Molecular Sequence Data; Penicillin-binding protein; Protein Structure, Secondary; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - isolation & purification; Recombinant Fusion Proteins - metabolism; Ribosomal Proteins - genetics; Ribosomal Proteins - isolation & purification; Ribosomal Proteins - metabolism; Sequence Alignment; Serine protease; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Spectroscopy, Fourier Transform Infrared; β-Lactamase
• ISSN: 1046-5928; 1096-0279
• DOI: 10.1016/j.pep.2005.08.006

LACTB is a mammalian mitochondrial protein sharing sequence similarity to the β-lactamase/penicillin-binding protein family of serine proteases that are involved in bacterial cell wall metabolism. The physiological role of LACTB is unclear. In this study we have subcloned the cDNA of mouse LACTB (mLACTB) and produced recombinant mLACTB protein in Escherichia coli. When mLACTB was expressed as an N-terminal GST fusion protein (GST-mLACTB), full-length GST-mLACTB protein was recovered by glutathione–agarose affinity chromatography as determined by MALDI-TOF mass spectrometry and immunoblotting. Expression of mLACTB as a C-terminal GST fusion protein or with either an N- or C-terminal His 6-tag resulted in proteolytic degradation of the protein and we were not able to detect full-length mLACTB. Analysis of GST-mLACTB by Fourier transform infrared spectrometry revealed the presence of α-helices, β-sheets and turns, consistent with a well-defined secondary structure. These results show that mLACTB can be expressed as a GST fusion protein in E. coli and suggest that GST-mLACTB was properly folded.