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 small protein based on mammalian O6-alkylguanine-DNA alkyltransferase (AGT). SNAP-tag substrates are derivatives of benzylpurines and benzylchloropyrimidines. 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.
Figure 1: Structure of SNAP-Cell Block (MW 338.2 g/mol)
Notes:
Please note that there is a constant turnover and resynthesis of proteins in the cell. After having blocked all existing SNAP-tag fusion proteins within the cell, new SNAP-tag fusion protein molecules may be synthesized in the meantime and may get labeled during incubation with a fluorescent SNAP-tag substrate. This will give the impression that the blocking was ineffective. In order to minimize these effects of protein synthesis and protein transport, cells may have to be treated with cycloheximide and incubation with the fluorescent SNAP-tag substrate may have to be performed at 4°C.Storage: SNAP-Cell Block should be stored at -20°C (long term) or at 4°C (short term). With proper storage at -20°C, SNAP-Cell Block is stable for at least three years dry or 3 months when dissolved in DMSO.For troubleshooting please refer to the instructions supplied with SNAP-Cell products as appropriate.
