Table 1.

Examples of Strategies for Engineering of Therapeutic Proteins

Issue Addressed		Engineering Strategy	Example Reference
Lack of posttranslational modifications in E. coli	Glycosylation	Expression without the glycosylation (only if the biological activity is not impaired)	IL-2 [3], IFN-β-1b [4]
		Mutation of residues on the surface to create more soluble protein	EPO [5]
		Mutation of glycosylation sites to cysteines to allow subsequent glycosylation in vitro	EPO [6]
	Proteolytic maturation	Expression in two separate strains or cleavage of the precursor in vitro	insulin [7]
	Disulfide bridge formation	Expression in the periplasmic space	hGH [8], proinsulin [9]
Protein stability		Decreasing number of free cysteine residues by mutation to alanine	IL-2 [10], IFN-β-1b [11]
		Deletion of the hydrophobic region	KGF [12]
Modulation of protein activity		Design of the rapid-acting or long-acting protein version	insulin [13-17]
		Enhanced activity by improved affinity to the target molecule	DNaseI [18]
		Design of protein consisting of a consensus sequence	IFN-α-con [19, 20]