Protein Tag Guide

Protein tags can be used for a variety of protein applications, including:

  • Protein secretion
  • Affinity purification
  • Epitope detection for western blots, FACS or immunohistochemistry
  • Chromatography
  • Increasing solubility
  • Reporter gene fusions to measure protein levels and activity

Oxford Genetics Ltd provides the largest collection of protein tags in the world, with over 1500 peptide tag variant plasmids for most research purposes. We can also easily create any new tag you need on request if we haven’t got the combination you need already. When choosing which protein tag to use it is important to consider your required application. Some tags are much more efficient than others for certain applications and the table below may help you decide which to use.

Typically, affinity tags are useful for protein purification, whilst solubility tags can be useful for increasing yields (but often also for purification). Epitope tags are typically useful for protein detection, but can also be used for purification but this is generally more expensive than using affinity resins because they require large amounts of antibody for purification.

As general rule you can normally find antibodies against most of the tags available, so technically they can all be used for detection and/or purification, but using certain methods for some tags can be much more expensive and some can produce less pure protein preparations.


Affinity Tags                                             

Tag Name Size Level of Affinity  Common Resins Relative Cost
Deca-Histidine (10His)  10 *** Talon or Ni-NTA *
Hexa-Histidine (6His) 6 *** Talon or Ni-NTA *
Strep 8 *** Strep-Tactin–Sepharose **
Glutathione-S-Transferase (GST) 218 ** GSH–Sepharose *
Maltose Binding Protein (MBP) 396 * Amylose *



Epitope Tags   


Tag Name Size Method of Purification 

Cost (antibody specific)

FLAG 8 Antibody Purification *** DYKDDDDK
C-Myc 10 Antibody Purification *** EQKLISEEDL
HA 9 Antibody Purification *** YPYDVPDYA
T7 11 Antibody Purification *** MASMTGGQQMG
V5 14 Antibody Purification *** GKPIPNPLLGLDST
S-tag 15 Antibody Purification *** KETAAAKFERQHMDS
Glu-Glu 9 Antibody Purification *** EYMPME
HSV 12 Antibody Purification *** QPELAPEDPEDC
VSV 11 Antibody Purification *** YTDIEMNRLGK
E-Tag 13 Antibody Purification *** GAPVPYPDPLEPR
Strep Tag 8 Antibody Purification *** WSHPQFEK


Reporter Tags            


Reporter Name

Ease of


Reporter Type Location Length (AAs)
FireFly Luciferase (FLuc) *** Luminescent Cystosol 549
Renilla Luciferase (RLuc) ** Luminescent Cystosol 311
iLumena Luciferase *** Luminescent Secreted 211
Beta Galactosidase (BetaGal) ** Colourimetric Cystosol 1047
Secreted Alkaline Phosphatase (SEAP) ** Colourimetric Secreted 520
Chloramphenicol Acetyl Transferase (CAT) * Colourimetric Cystosol 218
daGFP *** Fluorescent Cystosol 235
KrYFP *** Fluorescent Cystosol 235
FrCFP * Fluorescent Cystosol 235


If you require any further information regarding our product range then please contact us for more information.