SNAP-Cell® Block (bromothenylpteridine, BTP) is a non-fluorescent compound that blocks the reactivity of the SNAP-tag® in solution or in living cells. It can be used to generate inactive controls in live cell labeling experiments performed with SNAP-tag fusion proteins. SNAP-Cell Block is highly membrane permeable and once in the cell reacts with the SNAP-tag, irreversibly inactivating it for subsequent labeling steps.
The SNAP-tag protein labeling system enables the specific, covalent attachment of virtually any molecule to a protein of interest. The SNAP-tag is a protein based on human O6-alkylguanine-DNA alkyltransferase (hAGT). SNAP-tag substrates are fluorophores, biotin or beads conjugated to guanine or chloropyrimidine leaving groups via a benzyl linker. In the labeling reaction, the substituted benzyl group of the substrate is covalently attached to the SNAP-tag.
There are two steps to using this system: sub-cloning and expression of the protein of interest as a SNAP-tag fusion, and labeling of the fusion with the SNAP-tag substrate of choice. Expression of SNAP-tag fusion proteins is described in the instructions supplied with SNAP-tag plasmids. The labeling of SNAP-tag fusion proteins with SNAP-Cell substrates is described in the instructions supplied with SNAP-Cell substrates. The use of SNAP-Cell Block during the labeling of fusion proteins with SNAP-Cell substrates is described below.