The Difficult Of Eukaryotic Genes Expression By Bacteria

When bacteria are used to produce a eukaryotic protein, it is desirable to design the system so as to produce as large an amount of the protein as possible.

There are several such systems for proteins expression in E.coli. For instance, One system uses phage T7 RNA polymerase operating on a T7 promoter. Late in infection, phage T7 synthesizes enormous amounts of gene products from several sites termed late promoters. Because host chromosomal genes are not synthesized at this point, these products are the only proteins synthesized. The T7 RNA polymerase then transcribes this gene at high levels, resulting in high production of the factor VIII protein in the bacteria.

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Prokaryotic cells (bacteria, especially E. coli) are normally the preferred host for the expression of foreign proteins because they offer: Inexpensive carbon source requirements for growth, Rapid biomass accumulation, Amenability to high-cell density fermentation, and Simple process scale up.

However, a lack of post-translational machinery and production of inactive protein due to the formation of inclusion bodies. One disadvantage of using an organism such as E. coli for expression of eukaryotic genes is that it is a prokaryote, and therefore lacks the membrane-bound nucleus (and other organelles) found in eukaryotic cells. This means that certain eukaryotic genes may not function in E. coli as they would in their normal environment, which can hamper their isolation by selection mechanisms that depend on gene expression.

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