The GST-tagged protein specifically binds to glutathione immobilized to a matrix (e.g., agarose) and can be easily separated from a cell lysate by a bind-wash-elute procedure. The protocol can also be used to purify GST-tagged proteins from other expression systems, such as insect or mammalian cells.
How do you remove GST tag from fusion protein?
The fusion protein then is eluted under mild, non-denaturing conditions using reduced glutathione. If desired, the removal of the GST affinity tag is accomplished by using a site-specific protease recognition sequence located between the GST moiety and the target protein.
How can GST dimerization be reduced?
Strategies to prevent dimerization include modification of salt or pH, or the addition of a strong reducing agent such as dithiothreitol (DTT).
How does reduced glutathione GSH elute the GST tagged protein from the beads?
When reduced glutathione is immobilized through its sulfhydryl group to a solid support, such as cross-linked beaded agarose, it can be used to capture pure GST or GST-tagged proteins via the enzyme-substrate binding reaction.
What does GST protein do?
The primary role of GSTs is to detoxify xenobiotics by catalyzing the nucleophilic attack by GSH on electrophilic carbon, sulfur, or nitrogen atoms of said nonpolar xenobiotic substrates, thereby preventing their interaction with crucial cellular proteins and nucleic acids.
How do you reuse GST beads?
Glutathione Sepharose 4B may be regenerated for re-use by washing the gel with 2–3 bed volumes of alternating high pH (0.1 M Tris-HCl + 0.5 M NaCl, pH 8.5) and low pH (0.1 M sodium acetate + 0.5 M NaCl, pH 4.5) buffers. This cycle should be repeated 3 times followed by re-equilibration with 3–5 bed volumes of 1X PBS.
How is GST tag removed?
Removal of the GST tag is often necessary to be able to perform functional or structural studies of the target protein. Tagged proteins containing a PreScission Protease, thrombin, or Factor Xa recognition site can be cleaved either while bound to Glutathione Sepharose® or in solution after elution.
How do you fuse proteins?
Naturally occurring fusion genes are most commonly created when a chromosomal translocation replaces the terminal exons of one gene with intact exons from a second gene. This creates a single gene that can be transcribed, spliced, and translated to produce a functional fusion protein.
Does imidazole inhibit thrombin?
And as long as the imidazole doesn’t inhibit the thrombin, don’t worry about it until you get to the final purification steps, which, I presume, will be chromatography…
How do you elute protein from GST beads?
To elute the protein from the GST tag and agarose bead, add 10µl of thrombin (10 units) per mg GST tagged protein. 2. Mix gently and incubate at room temperature for 2-16 hours.
Why do we need reduced glutathione?
The tripeptide can exist intracellularly in either an oxidized (GSSG) or reduced (GSH) state. Maintaining optimal GSH:GSSG ratios in the cell is critical to survival, hence, tight regulation of the system is imperative. A deficiency of GSH puts the cell at risk for oxidative damage.
Why does GST bind to glutathione?
Specifically, the function of GSTs in this role is twofold: to bind both the substrate at the enzyme’s hydrophobic H-site and GSH at the adjacent, hydrophilic G-site, which together form the active site of the enzyme; and subsequently to activate the thiol group of GSH, enabling the nucleophilic attack upon the …
What is the role of GST in protein purification?
Second, GST can be affinity-purified without denaturation because it binds to immobilized glutathione, which provides the basis for simple purification. Consequently, GST fusion proteins are routinely used for antibody generation and purification, protein-protein interaction studies, and biochemical analysis.
What is the best PBS buffer for GST fusion protein?
PBS lysis buffer, freshly prepared PBS for GST fusion protein preparation, ice cold PBS with protease inhibitors, freshly prepared Tris-Cl (50 mM, pH 8.0) containing 20 mM reduced glutathione (Sigma, Amersham)
Why was GST originally selected as a fusion moiety?
GST was originally selected as a fusion moiety because of several desirable properties. First and foremost, when expressed in bacteria alone, or as a fusion, GST is not sequestered in inclusion bodies (in contrast to previous fusion protein systems).
How can GST be affinity-purified without denaturation?
Second, GST can be affinity-purified without denaturation because it binds to immobilized glutathione, which provides the basis for simple purification.
