SNAP recombinant proteins are engineered proteins based on the SNAP-tag, a self-labeling enzyme that facilitates covalent attachment of functional groups to proteins of interest. The SNAP-tag is derived from the human DNA repair enzyme O^6-alkylguanine-DNA alkyltransferase (hAGT). In recombinant forms, the SNAP-tag is fused to a protein of interest, allowing for specific and efficient labeling with various substrates, including fluorescent dyes, biotin, and other functional moieties.

Technical Content

Mechanism

The SNAP-tag covalently binds to benzylguanine (BG) derivatives. When a SNAP-tagged protein is exposed to a BG-linked substrate, the tag transfers the benzyl group from the substrate to a cysteine residue within the SNAP-tag, resulting in a stable and irreversible covalent bond.

Applications

• Protein labeling: SNAP-tag enables site-specific labeling of proteins in live cells or in vitro, useful for imaging, tracking, or purification.
• Protein interactions: SNAP recombinant proteins facilitate the study of protein-protein interactions via co-localization studies or FRET (Förster Resonance Energy Transfer).
• Bioconjugation: SNAP-tag can be used to conjugate proteins to various molecules, including nanoparticles, surfaces, or other biomolecules for biochemical assays and drug delivery systems.

Advantages

• Specificity: High specificity of the SNAP-tag to BG derivatives ensures minimal off-target effects.
• Versatility: The SNAP-tag can be fused to either the N-terminus or C-terminus of the target protein without disrupting its function.
• Compatibility: SNAP-tag is compatible with both prokaryotic and eukaryotic expression systems.

Limitations

• Size: The SNAP-tag adds approximately 20 kDa to the fusion protein, which may affect the biological function of the target protein in some cases.
• Reaction Kinetics: The labeling reaction can be slow under certain conditions, requiring optimization of incubation time and temperature.