Fusion tags for recombinant protein expression and purification in structural and functional studies

Protein purification is a critical prerequisite for biochemical, biophysical, and structural analyses. Although proteins can be isolated from their native environments, this approach is often limited by low yield and heterogeneity. Recombinant protein expression provides an efficient alternative, allowing the production of large quantities of target proteins in diverse host systems. To overcome challenges in yield, solubility, stability, and recovery, fusion tags are widely employed. These tags not only improve expression levels but also facilitate purification through affinity-based methods, and in some cases, contribute directly to functional or structural characterization. This review provides an overview of commonly used fusion tags, and considerations for selecting appropriate tags based on experimental needs and the target proteins. By enabling streamlined expression and purification, fusion tags expand opportunities to investigate protein structures, folding, and interaction networks. Such advances ultimately enhance our understanding of protein function and support the rational design of novel therapeutics.