Protein Expression Prokaryotic cells - E. coli (MPMV) Pr78Gag

Protein expression refers to the techniques in which a protein of interest is synthesized, modified or regulated in cells. The blueprints for proteins are stored in DNA which is then transcribed to produce messenger RNA (mRNA). mRNA is then translated into protein. In prokaryotes, this process of mRNA translation occurs simultaneously with mRNA transcription. In eukaryotes, these two processes occur at separate times and in separate cellular regions (transcription in nucleus and translation in cytoplasm). Recombinant protein expression utilizes cellular machinery to generate proteins, instead of chemical synthesis of proteins as it is very complex. Proteins produced from such DNA templates are called recombinant proteins and DNA templates are simple to construct. Recombinant protein expression involves transfecting cells with a DNA vector that contains the template. The cultured cells can then transcribe and translate the desired protein. The cells can be lysed to extract the expressed protein for subsequent purification. Both prokaryotic and eukaryotic protein expression systems are widely used. The selection of the system depends on the type of protein, the requirements for functional activity and the desired yield. These expression systems include mammalian, insect, yeast, bacterial, algal and cell-free. Each of these has pros and cons. Mammalian expression systems can be used for transient or stable expression, with ultra high-yield protein expression. However, high yields are only possible in suspension cultures and more demanding culture conditions. Insect cultures are the same as mammalian, except that they can be used as both static and suspension cultures. These cultures also have demanding culture conditions and may also be time consuming. Yeast cultures can produce eukaryotic proteins and are scalable, with minimum culture requirements. Yeast cultures may require growth culture optimization. Bacterial cultures are simple, scalable and low cost, but these may require protein specific optimization and are not suitable for all mammalian proteins. Algal cultures are optimized for robust selection and expression, but these are less developed than other host platforms. Cell-free systems are open, free of any unnatural compounds, fast and simple. This system is however, not optimal for scaling up.

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Found 1 matching solution for this experiment

pET28b-MPMVGag

Tahir Aziz Rizvi, Department of Microbiology & Immunology, Colle

Upstream tips	Protocol tips	Downstream tips
	Large scale recombinant Pr78Gag-His6-tagged protein expression was performed by inoculating a single colony into 25 ml LB media containing kanamycin antibiotic (50 µg/ml), and cultured at 37 °C, overnight with shaking at 200 rounds per minute (rpm). The overnight culture was used to inoculate 500 ml LB media containing kanamycin (50 µg/ml) in a 2-liter baffled Erlenmeyer flask. The culture was grown at 28 °C until an OD600 nm of approximately 0.6 was reached. Protein expression was induced with the addition of 0.4 mM IPTG, and the cells were grown for a further 4 h at 28 °C.	Cells were harvested by centrifugation (6,300 g) at 4 °C for 15 minutes and cell pellets were stored frozen at −80 °C.

Protocol tips
Large scale recombinant Pr78Gag-His6-tagged protein expression was performed by inoculating a single colony into 25 ml LB media containing kanamycin antibiotic (50 µg/ml), and cultured at 37 °C, overnight with shaking at 200 rounds per minute (rpm). The overnight culture was used to inoculate 500 ml LB media containing kanamycin (50 µg/ml) in a 2-liter baffled Erlenmeyer flask. The culture was grown at 28 °C until an OD600 nm of approximately 0.6 was reached. Protein expression was induced with the addition of 0.4 mM IPTG, and the cells were grown for a further 4 h at 28 °C.
Downstream tips
Cells were harvested by centrifugation (6,300 g) at 4 °C for 15 minutes and cell pellets were stored frozen at −80 °C.

Publication protocol 1 Relevant paper

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