Protein Tag Antibodies

Protein Tag Antibodies

What are Protein Tags?

Protein tags are peptide sequences incorporated into the structure of protein. They facilitate easier detection and purification of proteins. Protein Tags often do not interfere with protein function and can be easily removed with the use of proteases. They may be used for detection purposes by allowing for the visualization of proteins via immunostaining techniques (immunocytochemistry, immunohistochemistry). They may also be used for the large-scale purification of proteins from cell lysates.

Figure 1. Immunoprecipitation of over-expressed Myc-tagged protein in 293T cells incubated using Myc-tag antibody (CABE010). A mock served as negative control and over-expressed 293T cell lysate served as positive control.


Types of Protein Tags

Protein Tag Type Description Common Applications

GFP (Green Fluorescent Protein)

Fluorophore

Isolated from the jellyfish Aequorea victoria. Yields a green colour when exposed to blue or ultraviolet (UV) light.

Reporter assays, fluorescence microscopy, protein colocalization. macrophotography, transgenics.

RFP (Red Fluorescent Protein)

Fluorophore

The original RFP was isolated from Discosoma, and named DsRed. Yields a red-orange colour when excited.

Protein localization studies (detection), protein purification, optical imaging.

T7 (T7 RNA Polymerase)

Fluorophore

RNA polymerase from the T7 bacteriophage that catalyzes the formation of RNA from DNA in the 5'→ 3' direction.

Protein detection and expression - tag in many expression vectors (based on T7 RNA polymerase expression system).

mCherry

Fluorophore

Member of the mFruits family of monomeric red fluorescent proteins. Derived from DsRed of Discosoma sea anemones.

Fluorescence microscopy, long-wavelength hetero-FRET (fluorescence resonant energy transfer) , bacteria labeling.

DDDDK

Fluorophore

Hydrophillic polypeptide tag.

Protein localization via immunofluorescence, SDS-Page.

HA

Peptide

Tag derived from hemagglutinin 98-106 amino acids in length. Hemagglutinin is a class I fusion protein found on the surface of influenza viruses.

Protein detection and purification, epitope tag in expression vectors.

His

Peptide

Tag derived from the amino acid histidine. Vary in length between 4 and 10 residues, with the most common His-tag being 6 residues in length (Hexahistidine tag).

Detection of protein-protein interactions, protein purification via binding assays, fluorescent microscopy (fluorohistidine tags).

Myc

Peptide

Tag derived from the c-myc gene product.

Affinity Chromatography, cellulite localization studies by immunofluorescence, Protein detection by Western blotting.

GST (Glutathione-S-transferase)

Polyeptide

Large tag consisting of 220 amino acids (roughly 26 kDa).

Protein purification via pull-down assays.

TAP (Transporter associated with antigen processing)

Polyeptide

Consists of two Immunoglobulin G (IgG) binding domains from the Staphylococcus aureus surface protein, Protein A and a calmodulin-binding peptide (CBP).

Protein purification via protein A affinity chromatography.

Trx (Thioredoxin)

Polyeptide

Thioredoxin is normally involved in the reduction of oxidised cysteine residues as well as the cleavage of disulfide bonds. Used as a solubilization tag.

Assist protein folding, improve solubility of tagged protein.

V5

Polyeptide

Short epitope tag approximately 14 amino acids in length.

Protein detection and purification.

MBP (Maltose-binding protein)

Polyeptide

Protein tag expressed in E.Coli responsible for the uptake and efficient catabolism of maltodextrins. Approximately 42.5 kDa in length

Protein purification by affinity chromatography.


Advantages of Protein Tags

  • Protein tags can often improve the solubility of proteins - they can make insoluble proteins soluble.

  • Can be used to study protein localization in cells (fluorescent tags).
  • Allow for the easier purification of proteins, that without a tag, would be difficult to purify.

  • Can be used to distinguish similar proteins from one another.

  • Tags can be as easily removed as they are attached-proteases may be used to remove a protein tag. Protease treatment is a simple technique.

  • For greater purification a protein may be tagged with more than one tag. More purification steps in the process yields product of greater purity.

Figure 2. Immunofluorescence analysis of GFP transgenic 293T cells using GFP-Tag antibody (CABE011). Green: GFP expression. Blue: DAPI for nuclear staining.


What are Protein Tag Antibodies Used For?

Antibodies can be created with specificity against particular protein tags. Anti-Tag antibodies may be monoclonal or polyclonal, and may be used to detect and/or purify proteins which possess a tag.

Detection

  • Western Blot
  • Immunoprecipitation (IP)/Co-immunoprecipitation (Co-IP)
  • Immunostaining (Immunocytochemistry (ICC) Immunohistochemistry (IHC)

Purification

  • Affinity Chromatography

Advantages of Protein Tag Antibodies

  • Protein tag antibodies are extremely useful when there are no antibodies available for the target protein.

  • Useful when antibodies against target protein are not specific enough to provide accurate results. Anti-Tag antibodies are highly specific and non-reactive since they are normally synthesized in expression systems such as E.coli and viruses, and not in mammalian cells.

  • The same anti-tag antibody may be used to purify a wide range of proteins with the same tag.

Antibody Genie Protein Tag Antibodies

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