Bacterial transformation is a significant breakthrough in the field of molecular biology for cloning purposes. A variety of chemical and physical methods are utilized for enhancing bacterial competence. The present study was designed, via the consolidation of chemical and physical methods, to improve competence of cells for high transformation efficiency up to 10 9 transformants/µg of DNA. LB and SOC media and their supplemented combinations with osmotic agents (sucrose and glycine) were used to prepare electrocompetent cells of E. coli DH5α at temperatures of 25 and 37 °C, which were then subjected to electroporation. The results showed that cells grown in SOC medium showed high growth rates and increased transformation efficiencies as compared to LB, while media supplemented with osmotic agents also showed higher transformation proficiency as compared to the controls. In all combinations tested, the highest transformation efficiencies were observed in the cells grown in SOC-SG at 25 °C, i.e. 3.56 × 10 9 cfu/µg of DNA. This study provides valuable knowledge for low-budget biotechnology labs to prepare competent cells with efficiency comparable to commercially available competent cells.
Germin and germin-like proteins (GLPs) are a broad family of extracellular glycoproteins ubiquitously distributed in plants. Overexpression of Oryza sativa root germin like protein 1 (OsRGLP1) enhances superoxide dismutase (SOD) activity in transgenic plants. Here, we report bioinformatic analysis and heterologous expression of OsRGLP1 to study the role of glycosylation on OsRGLP1 protein stability and activity. Sequence analysis of OsRGLP1 homologs identified diverse N-glycosylation sequons, one of which was highly conserved. We therefore expressed OsRGLP1 in glycosylation-competent Saccharomyces cerevisiae as a Maltose Binding Protein (MBP) fusion. Mass spectrometry analysis of purified OsRGLP1 showed it was expressed by S. cerevisiae in both N-glycosylated and unmodified forms. Glycoprotein thermal profiling showed little difference in the thermal stability of the glycosylated and unmodified protein forms. Circular Dichroism spectroscopy of MBP-OsRGLP1 and a N-Q glycosylation-deficient variant showed that both glycosylated and unmodified MBP-OsRGLP1 had similar secondary structure, and both forms had equivalent SOD activity. Together, we concluded that glycosylation was not critical for OsRGLP1 protein stability or activity, and it could therefore likely be produced in Escherichia coli without glycosylation. Indeed, we found that OsRGLP1 could be efficiently expressed and purified from K12 shuffle E. coli with a specific activity of 1251 Units/mg. In conclusion, we find that some highly conserved N-glycosylation sites are not necessarily required for protein stability or activity, and describe a suitable method for production of OsRGLP1 which paves the way for further characterization and use of this protein.
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