GST-tag

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GST stands for glutathione-S-transferase, commonly used to create fusion proteins. The tag has the size of 220 aminoacids, which is compared to other tags, like the myc-, or the FLAG-tag quite big. It is fused to the N-terminus of a protein.

A GST-tag is often used to separate and purify proteins that contain the GST-fusion. GST-fusion proteins can be produced in E. coli, as recombinant proteins. The GST part binds its substrate, glutathione. Sepharose beads can be coated with glutathione, and such glutathione-sepharose beads bind GST-proteins. These beads are then washed, to remove contaminating bacterial proteins. Adding free glutathione to beads that bind purified GST-proteins will release the GST-protein in solution.