A novel epitope tag from rabies virus has versatile in vitro applications.

Fusion tag technology is an important tool for rapid separation, purification, and characterization of proteins. Combined with monoclonal antibodies, tag epitope systems can be rapidly adapted to many assay systems. A monoclonal antibody that reacts with the matrix protein of the rabies virus CVS-11 strain was reported. The epitope (termed M) targeted by this antibody contains only six amino acids. We examine whether this specific sequence epitope can be applied as a protein tag. We show ectopic expression of M-tagged proteins has little impact on cell viability or major signaling pathways. The M tag system can be used for western blotting, immunoprecipitation, immunofluorescence staining, and flow cytometry assays. The results indicate the specificity, sensitivity, and versatility of this novel epitope tag system are comparable to the widely used FLAG tag system, providing researchers with an additional tool for molecular analysis. KEY POINTS: • A short peptide (Pro Pro Tyr Asp Asp Asp) can be applied as a new tag. • The new epitope-tagging fusion system has no effect on the main cellular signaling pathway. • The epitope-tagging fusion system can be widely used for western blotting, immunoprecipitation, immunofluorescence, flow cytometry, etc.