Tagging peptides with affinity tags such as biotin is a frequently used strategy in life sciences research. Typically, these labels are removed by means of chemical reagents or enzymes, such as proteolysis or intron splicing. Tags are attached to proteins for different purposes. Affinity tags are added to proteins so that they can be purified from their original biologics using affinity techniques. These proteins include chitin binding protein (CBP), maltose binding protein (MBP), Strep-Tag and glutathione S-transferase (GST). Poly (His) tag is a widely used protein tag, which binds to the metal matrix. Peptide labeling (such as HA, myc, FLAG, HIS6) is one of the most commonly used methods for the detection, purification or immobilization of proteins.
Types of Tag
- The Flag tagging system uses a short hydrophilic octaamino acid peptide (DYKDDDDK) to fuse to the target protein; its purification conditions are non-denatured so all active fusion proteins can be purified.
- Myc tag (sequence: EQKLISEEDL) has been successfully used in WB hybridization, immunoprecipitation IP and flow cytometry. Therefore, it can be used to detect the expression of recombinant protein in bacteria, yeast, insect cells, and lactation cells.
- The HA tagging system uses an HA (influenza hemagglutinin epitope: YPYDVPDYA) peptide to fuse into the target protein. HA tags can be located at the C-terminal or N-terminal of proteins. The system has been widely used in a variety of cell types, and the corresponding HA tag antibodies have also been widely used.
- His tag is a short peptide composed of six histidines (His-His), which is specially designed for the adsorption and purification of recombinant proteins. Because of its small molecular weight and easy separation and purification, it is the most widely used at present.
- GST labeling system has the characteristics of high expression rate of protein, convenient purification of expression products, and is conducive to the preparation of GST antibody. GST fusion protein is soluble in aqueous solution and can be extracted from bacterial lysate and obtained by affinity chromatography under invariant conditions.
- The MBP (maltose binding protein) tag protein is 40 Ka in size and is encoded by the malE gene of E. coli K12. MBP can increase the solubility of fusion proteins overexpressed in bacteria, especially eukaryotic proteins. If the protein is expressed in bacteria, MBP can be fused to the N or C end of the protein. MBP antibody or expressed target protein-specific antibody can be used to detect the recombinant protein labeled by MBP tag.
Creative Peptides usually uses various tags in the synthesis of labeled peptides. Tags are usually attached to the N-terminal or C-terminal (through lysine or cysteine), but in principle, they can be placed anywhere. If necessary, the label can be separated from the peptide through the spacer. A variety of so-called connectors or spacer molecules are available in different lengths and polarities. Linkers can also be cut, for example, by reducing sensitive disulfide bonds.
References
- Christians, F. (2013). U.S. Patent No. 8,389,676. Washington, DC: U.S. Patent and Trademark Office.
- Dang, B., Mravic, M., Hu, H., Schmidt, N., Mensa, B., & DeGrado, W. F. (2019). SNAC-tag for sequence-specific chemical protein cleavage. Nature Methods, 16(4), 319.
