Table 7 A list of fusion tags used in insulin purification and their advantages

Five leader peptides engineered with different sequences

Improved peptide expression levels

Improved refolding yield, because the leader peptide affects protein conformation and hydrophobicity

Simultaneous removal of the N-fused sequence and the C-peptide by trypsin in a single step

Min et al. (2011)

Polyhistidine

For purification by metal chelate affinity chromatography (Astolfi et al. 2004; Mackin 1999; Redwan et al. 2007; Tikhonov et al. 2001; Yuan et al. 2015; Zimmerman and Stokell 2010)

As an easily observed indicator, using either RP-HPLC or SDS-PAGE to show that the N-terminal methionine and the rest of the poly-His affinity tag has been removed from the fusion protein (Mackin 2014)

To reduce the rate of peptide degradation by stabilizing the expressed peptide and prevent N-terminal degradation (Cowley and Mackin 1997; Mackin 2014)

Improved peptide expression levels due to increased stability from (His)₁₀ tag of leader peptide and the tendency to stay at the exterior of the proinsulin molecule because of its polarity (Sung et al. 1986)

Astolfi et al. (2004)

Cowley and Mackin (1997)

Mackin (1999)

Mackin (2014)

Mackin and Choquette 2003)

Redwan et al. (2007)

Sung et al. (1986)

Tikhonov et al. (2001)

Winter et al. (2002a, b)

Yuan et al. (2015)

Zimmerman and Stokell (2010)

Two synthetic IgG-binding domains (ZZ) derived from staphylococcal protein A

For purification by IgG-affinity chromatography

ZZ-tail is highly resistant to proteolysis

ZZ-tail contains no cysteine residues that could cause unwanted disulfide bridges

Improved peptide expression levels

Simultaneous removal of the N-fused sequence and the C-peptide by trypsin in a single step, without cleavage of the target protein

The solubilizing properties of ZZ enable in vitro product refolding at high protein concentrations

ZZ-tag is useful for the facile detection and quantitation of staphylococcal protein A (or its engineered domain) fusion proteins secreted to the growth medium using quantitative ELISA (Mergulhao et al. 2001)

Mergulhao et al. (2001)

Mergulhao et al. (2004)

Nilsson et al. (1996)

One synthetic IgG-binding domains (Z) derived from staphylococcal protein A

Z-tail is highly resistant to proteolysis

Using a single Z domain instead of the ZZ domain as a fusion partner led to the recovery of a 1.6-fold higher amount of PI after cleavage of the fusion tag, although no effect of the molecular size was seen on the secretion efficiency of the system

Mergulhao et al. (2004)