Table 1.

Overview of biological ligands employed as binding partners of affinity tags. The “Target protein” is a representative case and the reference listed is for the example target protein.

Biological ligand		Tag	Tag size	Tag sequence	Elution condition	Yield1 (%)	Purity2 (%)	Representative Target Protein	Application	Reference
Peptides and Proteins	Glutathione	GST	26 kDa	–	20 mM reduced glutathione	100	80	DNA topoisomerase type II	Purification and solubility	Singh et al. (2011)
	Calmodulin	CBP	26 aa	KRRWKKNFIAVSAANRFKKISSSGAL	2 mM EDTA	n.a.	High	Nicotinamide nucleotide transhydrogenase	Purification	Egorov et al. (2004)
	S protein (S-fragment RNAse A)	S-tag	15 aa	KETAAAKFERGHMDS	Proteolytic cleavage	Fair	High	Recombinant human interleukin-29	Purification	Li and He (2006)
	Streptavidin	Strep-tag	9 aa	SAWRHPQFGG	1 mM iminobiotin	n.a.	High	Fv fragment	Detection and purification	Schmidt and Skerra (1993)
		Nano tag	9–15 aa	DVEAWLGAR	2 mM d-biotin	90	71	Bovine heart fatty acid-binding protein (FABP)		Lamla and Erdmann (2004)
		SBP	38 aa	MDEKTTGWRGGHVVEGLAGELEQLRARLEHHPQGQREP	2 mM biotin	High	High	Maltose-binding protein		Keefe et al. (2001)
	Strep-Tactin (modified streptavidin)	Strep tag II	8 aa	WSHPQFEK	2.5 mM d-desthiobiotin	n.a	99	Human tissue transglutaminase		Schmidt and Skerra (2007)
	NeutraAvidin	AviD-tag	6 aa	DRATPY	500 μM biotin	High	High	Green fluorescent protein (GFP)		Gaj et al. (2007)
	IgG	Protein A (SpA)	14–31 kDa	–	Glycine-HCl pH 3	95	High	β-galactosidase	Purification	Nilsson et al. (1985)
		Z domain	7 kDa	–	0.3 M acetic acid, pH 3.1	High	High	Klenow fragment of DNA polymerase I		Nilsson et al. (1994)
	IgG/HAS	Protein G (SpG)	28 kDa	–	85 ºC 10 minute incubation	n.a.	90	DNA polymerase		Gräslund et al. (1997)
	Monoclonal antibody M1, M2	FLAG	8 aa	DYKDDDDK	150 mM glycine-HCl pH 3.5	60	95	Metal response element binding transcription factor-1 (MTF-1)	Detection and purification	Huyck et al. (2012)
	Monoclonal antibody 9E10	c-myc	10 aa	EQKLISEEDL	Western blot (detection)	–	–	Tobacco etch virus (TEV) protease		Geisbrecht et al. (2006)
	Anti-T7 monoclonal antibody	T7 tag	11 aa	MASMTGGQQMG	0.1 M citric acid, pH 2.2, 5 mM glycerophosphate,5 mM KF	High	n.a	SR protein		Cazalla et al. (2005)
	Monoclonal antibody 12 CA5	HA tag	9 aa	YPYDVPDYA	0.85 M KCl	n.a.	High	Transcription factor IID		Carey et al. (2010)
	Polyol responsive monoclonal antibodies	Softag 1	13 aa	SLAELLNAGLGGS	0.7 M NaCl and 30% propylene glycol	n.a	High	GFP	Detection and purification	Thompson et al., 2003a, Thompson et al., 2003b
		Softag 2	14 aa	PTSPSYSPTSPSYS	0.5 M ammonium sulphate and 30% ethylene glycol	n.a.	High	RNA polymerase II		Thompson et al. (1990)
		Softag 3	8 aa	TKDPSRVG	75 M ammonium sulphate and 40% propylene glycol	n.a	n.a	GFP		Duellman et al. (2004)
Carbohydrates	Cross-linked amylose	MBP	42 kDa	–	10 mM Maltose	100	75	Tyrosine hydroxylase	Purification and solubility	Higgins et al. (2012)
	Cellulose	Cellulose binding protein	100 kDa	–	Pure water	80	High	Red fluorescent protein	Purification	Wan et al. (2011)
	Chitin	Chitin binding domain	5 kDa	–	Thiol induced self-cleavage	n.a.	99	Phosphite Dehydrogenase	Purification	Guan et al. (2013)
	Starch	Starch binding domain	133 aa	–	10 mM glycine-NaOH pH 11	86	90	Enhanced GFP	Purification	Lin et al. (2009)

¹ Yield—Recovery of pure protein; ² Purity—The purity of eluted proteins was evaluated by SDS-PAGE electrophoresis; GST—Gluthatione-S-transferase; CBP—calmodulin binding peptide; SPB—strepdavidin-binding peptide; IgG—immunoglobulin G; HSA—human serum albumin; HA—hemaglutinin antigen; MPB—maltose binding protein.