Selection Guide: Peptide Tags

Do you know which tag is best for your protein? Explore the options below to choose the best tag for your protein and application.

His Tag

The most versatile tag for protein purification

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Features When to Use When Not to Use
  • Distinct types of his tags are available, including the 6xHN tag (12 amino acids)
  • Most common affinity tag used to purify proteins
  • Binds to coordinated metals such as Ni2+ or Co2+
  • His-tagged proteins can be eluted with imidazole or low pH buffer
  • A his tag can be incorporated on either the N- or C-terminus
  • Can be expressed in bacterial, yeast, mammalian, and baculovirus-infected insect cells or in vitro
  • When a small tag is required to minimize its effect on protein function
  • When a low metabolic load is needed to maintain normal cell physiology and/or to increase protein expression
  • When a high capacity affinity resin is needed to increase yields and reduce costs
  • To reduce the cost of affinity purification by using an inexpensive resin
  • To reduce the cost of affinity purification by using a resin that can be regenerated multiple times
  • When the choice to purify a protein under native or denaturing conditions is needed
  • When mild elution conditions are necessary
  • For large-scale and HTP purifications
  • To study protein-protein or nucleic acid-protein interactions involving an immobilized his-tagged protein
  • When the tagged protein sample is in the presence of other metals or chelating reagents (EDTA)
  • When eluting proteins with imidazole buffers will interfere with downstream processes such as crystallography or NMR applications (elution with low pH buffers or desalting may overcome this issue)
  • When high concentrations of reducing agents (DTT) are necessary
  • When trying to purify metalloproteins

FLAG (DYKDDDDK) Tag

A common, well-characterized hydrophilic tag

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Features When to Use When Not to Use
  • Small peptide tag (8 amino acids)
  • Binds to the Anti-DYKDDDDK Antibody
  • FLAG-tagged proteins can be eluted with low pH buffer or sample buffer
  • A FLAG-tag can be incorporated on either the N- or C-terminus
  • Can be expressed in bacterial, yeast, mammalian, and baculovirus-infected insect cells
  • When a small tag is required to minimize its effect on protein function
  • When a low metabolic load is needed to maintain normal cell physiology and/or to increase protein expression
  • When a hydrophillic tag is required
  • When highly specific detection is necessary
  • When purification of highly pure protein at very low yields is acceptable
  • To monitor recombinant protein expression in bacterial, yeast, mammalian, or insect cells
  • For co-immunoprecipitation studies, Western blots, and flow cytometry
  • To monitor subcellular localization of the tagged protein in mammalian cells
  • When an inexpensive purification resin is needed
  • When low pH elution conditions can damage the target protein or affect its functionality (This issue can be overcome by competitive elution with FLAG peptide)
  • For applications requiring a resin with a high binding capacity or high yields
  • When matrix stability/shelf life is a factor
  • For large-scale and HTP purifications
  • When regeneration of the matrix is desired

Myc Tag

A small, immunoreactive tag—ideal for Co-IP & Westerns

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Features When to Use When Not to Use
  • Small peptide tag (11 amino acids)
  • Binds to the c-Myc Monoclonal Antibody
  • Myc-tagged protein can be eluted with low pH buffer or sample buffer
  • A Myc-tag can be incorporated on either the N-terminus, the C-terminus, or internally
  • Can be expressed in bacterial, yeast, mammalian, and baculovirus-infected insect cells
  • When a small tag is required to minimize its effect on protein function
  • When a low metabolic load is needed to maintain normal cell physiology and/or to increase protein expression
  • To monitor recombinant protein expression in bacterial, yeast, mammalian, or insect cells
  • For co-immunoprecipitation studies, Western blots, and flow cytometry
  • To monitor subcellular localization of the tagged protein in mammalian cells
  • When an inexpensive purification resin is needed
  • When low pH elution conditions can damage the target protein or affect its functionality
  • For applications requiring a resin with a high binding capacity or high yields
  • When matrix stability/shelf-life is a factor
  • For large-scale and HTP purifications
  • When regeneration of the matrix is desired

HA Tag

Ideal for Co-IP and Westerns—unlikely to interfere with the function of your protein

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Features When to Use When Not to Use
  • Small peptide tag (9 amino acids)
  • Binds to the HA Tag Polyclonal Antibody
  • An HA-tag can be incorporated on either the N-terminus, the C-terminus, or internally
  • Can be expressed in bacterial, yeast, mammalian, and baculovirus-infected insect cells
  • When a small tag is required to minimize its effect on protein function
  • When a low metabolic load is needed to maintain normal cell physiology and/or to increase protein expression
  • To monitor recombinant protein expression in bacterial, yeast, mammalian, or insect cells
  • For co-immunoprecipitation studies and Western blots
  • To monitor subcellular localization of the tagged protein in mammalian cells
  • As an affinity tag to purify tagged protein

GST Tag

Binds with high affinity and specificity

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Purify

GST-Tag Resins >
Features When to Use When Not to Use
  • Large protein tag (glutathione S-transferase, 26 kDa protein)
  • Binds to glutathione
  • GST-tagged proteins can be eluted with reduced glutathione
  • A GST-tag can be incorporated on either the N- or C-terminus
  • Can be expressed in bacterial, yeast, mammalian, and baculovirus-infected insect cells
  • To reduce the cost of affinity purification by using an inexpensive resin
  • To reduce the cost of affinity purification by using a resin that can be regenerated multiple times
  • When mild elution conditions are necessary
  • To protect some recombinant proteins from intracellular protease cleavage
  • When it is necessary to use a tag that may enhance the solubility of the tagged protein
  • When removal of the tag is necessary
  • To study protein-protein or protein-nucleic acid interactions
  • To use as an antigen for immunology or vaccination studies
  • When the protein needs to be purified under strong reducing conditions
  • When a low metabolic load is needed to maintain normal cell physiology and/or to increase protein expression
  • When a small tag is required
  • When a homodimeric protein tag is not suitable
  • When trying to isolate an oligomeric protein
  • When purification under denaturing conditions is required
  • When the target protein contains disulfides which may be reduced by the elution buffer