The Flag tag can be located at the c end or the n end of the protein. The system has been widely used in various cell types, including bacteria, yeast and mammalian cells, and the corresponding Flag tag antibodies have also been widely used. Because the purification conditions of Flag tag system are non-denatured, all active fusion proteins can be purified. The addition of enterokinase can remove the Flag tag, and the five amino acid residues at the C-terminal of enterokinase specific recognition peptide sequence.
Flag antibody can be used to detect the expression and intracellular localization of the fusion expression protein with Flag tag, and to purify, qualitatively or quantitatively detect the fusion expression protein of Flag. Fusion tags can be divided into two categories according to their relative molecular weights: protein macromolecules and polypeptide small fragments. The use of fusion tags can simplify the purification process of protein, control the fixed spatial orientation of protein and facilitate detection, visualize biological events in vivo, increase the yield of recombinant protein and enhance the solubility and stability of recombinant protein.
His tag is a short peptide composed of six histidines (his-his-his-his-his), which is specially used to adsorb and purify recombinant proteins. Because of its small molecular weight and easy separation and purification, His fusion tag has many obvious advantages compared with other tags, and it is the most widely used fusion tag for purification at present. Using His tag, an efficient detection and purification system based on fusion protein can be established.
His antibody can be used to detect the expression and intracellular localization of the fusion expression protein with His tag, and to purify, qualitatively or quantitatively detect the fusion expression protein of His. With the discovery of more and more new genes, gene fusion protein expression system has been widely used because of its remarkable advantages in the research of newly discovered protein. Among them, GST labeling system has the characteristics of high protein expression, convenient purification of expression products and favorable preparation of GST antibodies. GST fusion protein can be dissolved in water solution, extracted from bacterial lysate and obtained by affinity chromatography without denaturation. GST fusion protein can be cleaved by site-specific protease to remove GST protein. Fusion protein is also a very good strong immunogen, so it is easy to prepare antibodies against new proteins. It is precisely because of the above advantages that the commercial GST fusion protein expression system and GST tag antibody system are still widely used.
In recent years, the expression and purification system of glutathione S transferase GST has been more widely used in prokaryotic expression system. When using GST fusion expression system to express foreign genes, it is very important to detect and purify the fusion expression products, including the application of GST tag antibody. Commonly used tags are GFP, HA, Flag, His, GST, etc. Among them, green fluorescent protein (GFP) is a kind of protein, which was first discovered by Shimomura et al. in Aequorea victoria in 1962. Protein produced by its gene will emit green fluorescence under the excitation of light in the blue wavelength range.
GFP or its mutant EGFP is widely used to detect gene expression efficiency, and fusion expression with target protein is used to detect the expression and distribution of target protein. Generally speaking, GFP antibody can not only detect GFP or its appropriate mutant, but also detect the expression and intracellular localization of GFP or its appropriate mutant fusion expression protein, as well as purify, qualitatively or quantitatively detect GFP fusion expression protein.
GFP tags can be located at the C-terminal or N-terminal of protein. The system has been widely used in various cell types, including bacteria, yeast and mammalian cells, and the corresponding GFP labeled antibodies have also been widely used. In recent years, with the rapid development of protein genomics, the application of recombinant proteins has greatly increased. The recombinant hybrid contains affinity tags, such as GST, Myc, His, etc. , which can be used to assist the purification of target protein, has been widely used. It is generally believed that the use of fusion protein is helpful to the purification and detection of recombinant protein. In 1985, a mouse anti-c-myc tag antibody was developed and used as an immunochemical reagent in the fields of cell biology and protein engineering. Myc tag (sequence: EQKLISEEDL) has been successfully applied to 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 mammalian cells.
By coupling the antibody labeled by Myc to the agarose activated by divinylsulfone, the recombinant protein of Myc can be affinity purified. Myc tags can be placed at the C- terminal or N- terminal, but the low pH elution conditions of the recombinant protein of Myc often reduce the activity of the protein, so the Myc tag system is widely used for detection, but rarely used for purification. The use of fusion tags, such as HA and His tags, can simplify the purification process of protein, control the fixed spatial orientation of protein and facilitate detection, visualize biological events in vivo, increase the yield of recombinant protein, and enhance the solubility and stability of recombinant protein. Commonly used tags are myc, HA, Flag, His, GST, etc. Among them, HA tag system uses HA (affecting hemagglutinin epitope: ypydvpdya) short peptide to fuse with target protein.
The HA tag can be located at the C-end or N-end of protein. The system has been widely used in many cell types, and the corresponding HA tag antibodies have also been widely used. Antibodies labeled with HA can specifically recognize fusion proteins labeled with HA at C- terminal or N- terminal.