Why did the rHuEPO gene expression in E. coli fail to increase erythrocyte production when injected into humans?

• A. E. coli cannot produce any proteins
• B. E. coli cannot glycosylate EPO as required
• C. E. coli lacks the gene for EPO
• D. E. coli does not secrete EPO into the bloodstream

Answer: (B)

The rHuEPO gene expression in E. coli failed to increase erythrocyte production in humans primarily because E. coli cannot glycosylate EPO as required. Erythropoietin (EPO) is a glycoprotein, meaning that it undergoes post-translational modifications, specifically glycosylation, in order to achieve its proper structure and functionality. Glycosylation is essential for the stability, activity, and overall effectiveness of EPO within the human body.

While E. coli can successfully produce proteins, it lacks the necessary cellular machinery for glycosylation that is present in eukaryotic cells. Therefore, the EPO produced in E. coli would not have the correct post-translational modifications to function appropriately in humans. This underscores the importance of using appropriate expression systems that can mimic the required modifications when producing complex proteins like EPO for therapeutic use.