Final answer:
The GST tag in GST-DHFR-His is located at the N-terminus of the fusion protein, used in affinity chromatography for protein purification, with the His tag at the C-terminus.
Step-by-step explanation:
The GST tag is located on the N-terminus of the GST-DHFR-His fusion protein. It is a peptide sequence that is added to proteins to simplify the purification process through affinity chromatography. The GST (Glutathione S-transferase) tag binds to glutathione, which is immobilized on a chromatography column, allowing for ease of purification. Following the GST tag is the dihydrofolate reductase (DHFR) enzyme, and at the C-terminus of the protein, there is a His (Histidine) tag, which can also be used for purification through nickel affinity chromatography.
The use of multiple tags, like the GST tag and the His tag, provides researchers with options for the purification process and can improve the overall yield and purity of the protein of interest. This strategy is commonly employed in the field of molecular biology, where proteins are regularly engineered for study and practical applications.