Protein Expression: Eukaryotic vs. Prokaryotic Cells

Why is it difficult to express eukaryotic proteins in prokaryotic cells?

A) Presence of introns in eukaryotic genes and lack of splicing machinery in prokaryotic cells.

B) Need for post-translational modifications in eukaryotic proteins not present in prokaryotic cells.

Answer:

Both A) Presence of introns in eukaryotic genes and lack of splicing machinery in prokaryotic cells, and B) Need for post-translational modifications in eukaryotic proteins not present in prokaryotic cells are correct.

When attempting to express eukaryotic proteins in prokaryotic cells, several challenges arise due to the differences in genetic and biochemical mechanisms between these two cellular systems. One significant challenge is the presence of introns in eukaryotic genes. Eukaryotic genes contain non-coding regions known as introns that are removed during mRNA processing through a process called splicing. However, prokaryotic cells lack the complex splicing machinery required to accurately remove introns, which can result in non-functional or improperly processed transcripts when attempting to express eukaryotic genes directly in prokaryotic hosts.

Additionally, eukaryotic proteins often require post-translational modifications such as glycosylation, phosphorylation, and disulfide bond formation. These modifications are essential for the proper folding, stability, and biological activity of the proteins. However, prokaryotic cells do not possess the same enzymatic machinery as eukaryotic cells for these modifications. As a result, even if the gene is successfully transcribed and translated in a prokaryotic cell, the resulting protein may lack crucial modifications necessary for its functionality.

The combination of introns in eukaryotic genes and the need for post-translational modifications presents significant hurdles in the successful expression of eukaryotic proteins in prokaryotic cells. Strategies such as codon optimization and the use of specialized expression vectors are often employed to overcome these challenges and achieve successful heterologous protein expression.