FAQ: How specific is the binding of substrate to the SNAP-tag®?

This reaction is highly specific as it involves recognition of the benzylguanine substrate by the active site of the tag, those expressed SNAP-tag fusion proteins can be specifically labeled even in the presence of complex protein mixtures such as found in cells or in cleared bacterial lysates. The benzyl guanine substrate forms a covalent bond with Cys 145 of the tag (Tirat et al, Int J Biol Macromol, 2006. PMID: 16503347