The ACP-tag and MCP-tag protein labeling technologies are based on an enzyme-catalysed post-translational modification. Recombinant target protein that is fused to an acyl carrier protein (ACP), is labeled specifically with CoA derivatives, catalyzed by the phosphopantetheinyl transferase ACP Synthase (1). The ACP-tag is small, only 8 kDa (2). MCP-tag, a mutant of ACP-tag, is labeled by the phosphopantetheinyl transferase SFP Synthase but not by ACP Synthase, thereby permitting selective simultaneous labeling in a sample.
Membrane proteins are challenging to study given their hydrophobic nature, generally low native abundance and intrinsic instability (3,4). Regardless, half of all protein drug targets are membrane proteins. For imaging, most fluorescent proteins (i.e. GFP) cannot specifically visualize cell surface subpopulations. However, the ACP-tag/MCP-tag system is a cell surface-specific system since all of its substrates are non-cell permeable. It can specifically label subpopulations of target protein expressed on cell surface using non-cell permeable substrates (5). This approach permits discrimination of different populations of a cell surface protein: those properly translocated to the plasma membrane from those retained in the secretory pathway or already internalized (e.g. upon ligand binding).
- George, N., Pick, H., Vogel, H. et al. (2004) J. Am. Chem. Soc. 126, 8896. PMID: 15264811
- Yin, J., Straight, P.D., McLoughlin, S.M. et al. (2005) Proc. Natl. Acad. Sci. USA 102, 15815. PMID: 16236721
- Lacapère J-J, Pebay-Peyroula E, Neumann J-M, Etchebest C. (2007) Trends Biochem Sci. 32, 259–270. PMID: 17481903
- von Heijne G. (2007) J Intern Med. 261, 543–557. PMID: 17547710
- Keppler, A., Pick, H., Arrivoli, C. et al. (2004) Proc. Natl. Acad. Sci. USA 101, 9955. PMID: 15226507
SNAP-tag® is a registered trademark of New England Biolabs, Inc.