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
Express pET Express & Purify Kits »	Purify His60 nickel resin » TALON cobalt resins »	Detect 6xHis Monoclonal Antibody » 6xHN Polyclonal Antibody »
Features 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 to Use When a small tag is required to minimize effects 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 Not to Use 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

His tag
The most versatile tag for protein purification

Express
pET Express & Purify Kits »

Purify
His60 nickel resin »
TALON cobalt resins »

Detect
6xHis Monoclonal Antibody »
6xHN Polyclonal Antibody »

Features

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 to Use

When a small tag is required to minimize effects 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 Not to Use

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

Myc tag A small, immunoreactive tag—ideal for co-IP & western blots
Express pCMV-Myc & pCMV-HA Vector Set »	Purify c-Myc Monoclonal Antibody-Agarose Beads for IP »	Detect c-Myc Monoclonal Antibody »
Features 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 to Use When a small tag is required to minimize effects 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 Not to Use 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

Myc tag
A small, immunoreactive tag—ideal for co-IP & western blots

Express
pCMV-Myc & pCMV-HA Vector Set »

Purify
c-Myc Monoclonal Antibody-Agarose Beads for IP »

Detect
c-Myc Monoclonal Antibody »

Features

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 to Use

When a small tag is required to minimize effects 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 Not to Use

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 western blots—unlikely to interfere with the function of your protein
Express pCMV-Myc & pCMV-HA Vector Set »
Features 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 to Use When a small tag is required to minimize effects 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	When Not to Use As an affinity tag to purify tagged protein

HA tag
Ideal for co-IP and western blots—unlikely to interfere with the function of your protein

Express
pCMV-Myc & pCMV-HA Vector Set »

Features

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 to Use

When a small tag is required to minimize effects 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

When Not to Use

As an affinity tag to purify tagged protein

GST tag Binds with high affinity and specificity
Purify GST-tag resins »
Features 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	When to Use 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 Not to Use 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

GST tag
Binds with high affinity and specificity

Purify
GST-tag resins »

Features

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

When to Use

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 Not to Use

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

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