Proteinintag

Proteinintag refers to the practice of fusing a short peptide or larger protein tag to a protein of interest to aid detection, purification, localization, or functional studies. Tags can be encoded in the expression construct and are expressed as a single polypeptide with the target protein. The approach is widely used in biochemistry, cell biology, and biotechnology to facilitate downstream analyses and protein manipulation.

Common tag classes include affinity tags, solubility tags, fluorescent tags, and epitope tags. Affinity tags such as polyhistidine (His-tag), glutathione S-transferase (GST), and maltose-binding protein (MBP) enable purification by metal affinity or resin-based chromatography. Solubility tags like SUMO or NusA help improve soluble expression. Fluorescent tags, including GFP and its variants, enable live-cell imaging and localization studies. Epitope tags, such as FLAG, HA, and Myc, are primarily used for detection by antibodies in Western blotting, immunoprecipitation, or immunofluorescence.

Tag placement can be at the N- or C- terminus of the target protein, and in some cases internal insertion is possible. Tags are often separated from the protein of interest by a protease cleavage site (for example TEV or HRV 3C) to allow tag removal after purification or analysis. However, tags can affect folding, activity, localization, or interaction with partners, so the choice of tag and its position requires optimization.

Applications include recombinant protein purification, localization studies, interaction assays, and mass spectrometry workflows. While tags simplify many workflows, researchers balance convenience against potential functional perturbations and choose tag strategies accordingly.