The SNAP-tag® system is based on a DNA repair enzyme, O6-alkylguanine-DNA alkyltransferase (AGT). It allows for multiple substrate options to enable color changes. It is highly temperature and fixation stable and can be used in vitro or in vivo. The substrate consists of two parts; the benzylguanine group and the functional group, which can be a fluorophore, biotin or bead. During the labeling reaction, the substituted benzyl group covalently attaches to the SNAP-tag releasing free guanine. Once the fluorophore is coupled to the desired protein, the label fluoresces permitting visualization in living or fixed cells.
SNAP-tag® is a registered trademark of New England Biolabs, Inc.