Fusion tags can be a protein producer’s best friend. Attaching a tag like His₆, GST, or MBP can dramatically simplify purification and even improve solubility for tricky proteins. For instance, MBP or GST tags often help keep a normally aggregation-prone protein folded by acting as a chaperoning partner.
The trade-off?
Tags add extra length and may interfere with your protein’s function or crystallization if not removed. It’s important to choose a tag that suits your goal: His-tags are small and great for quick IMAC purification; larger tags like MBP increase yield of soluble protein but almost always require a cleavage step before final analyses.
Also consider tag placement – N-terminal vs C-terminal – as it can affect folding or activity. Use tags strategically: they’re extremely helpful tools, but plan ahead for whether (and how) to remove them later.