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  • SFP Synthase


    SFP Synthase (4´-phosphopantetheinyl transferase) catalyzes the covalent transfer of substituents from derivatized coenzyme A (CoA) to ACP- or MCP-tagged fusion proteins exposed on the surface of living cells. The 25 nmoles of SFP Synthase provided is sufficient to make 25 ml of a 1 µM ACP-tag or MCP-tag fusion protein labeling solution.

    The ACP-tag and MCP-tag are small protein tags (8 kDa) based on the acyl carrier protein. MCP-tag contains two mutations (D36-T36 and D39-G39). Both allow the specific, covalent attachment of virtually any molecule to a protein of interest. Substrates for labeling are derivatives of coenzyme A (CoA). In the labeling reaction, the substituted phosphopantetheine group of CoA is covalently attached to a conserved serine residue on the ACP-tag or the MCP-tag by a phosphopantetheine transferase (SFP Synthase or ACP Synthase). Having no cysteines, the ACP-tag and the MCP-tag are particularly suited for specifically labeling cell-surface proteins, and should be useful for labeling secreted proteins with disulfide bridges such as antibodies.

    While ACP Synthase (NEB #P9301) preferentially modify the ACP-tag, SFP Synthase preferentially modify the ACP-tag, SFP Synthase will modify both ACP-tag and MCP-tag. This principle can be employed for sequential dual labeling of two different proteins that localize to the cell surface. Cells co-expressing one ACP-tag fusion protein and one MCP-tag fusion protein can be incubated with ACP Synthase and one CoA substrate followed by labeling with SFP Synthase and a different CoA substrate.

    There are two steps to using this system: cloning and expression of the protein of interest as an ACP-tag or MCP-tag fusion, and labeling of the fusion protein using the SFP Synthase with the CoA substrate of choice. In this document, the labeling of fusion proteins with CoA substrates is described. The cloning of ACP-tag or MCP-tag protein fusions is described in the documentation supplied with the ACP-tag or the MCP-tag plasmids.

    Figure 1:
    SFP labeling reaction

    Product Source

    An E. coli strain carrying the cloned B.subtilis gene for 4´- phosphopantetheinyl transferase (SFP).

    Reagents Supplied

    The following reagents are supplied with this product:

    Store at (°C)Concentration
    1M MgCl2

    Properties and Usage

    Storage Temperature


    Storage Conditions

    50 mM HEPES
    150 mM NaCl
    1 mM DTT
    50% Glycerol
    pH 7.4

    Heat Inactivation


    Quality Control

    Quality Control Assays

    • Cellular Protein Labeling (Blocking Assay):
      The blocking compound is pre-incubated with cells  expressing the target protein followed by labeling of the target protein.  No labeling is detected by fluorescence microscopy
    • In Vitro Protein Labeling:

      The product is tested in an in vitro protein labeling reaction. After incubation the labeled product is visualized on SDS-PAGE by fluorescent detection and verified by mass spectrometry.


    1. Storage: SFP Synthase is stable for at least 2 years when stored at -20°C.

    Supporting Documents

    Material Safety Datasheets



    1. What is the ACP-tag?
    2. How does it work?
    4. What linker type and length would you recommend?
    6. Are ACP-tag substrates stable to fixation?
    1. Instructions for Use with SFP Synthase (P9302)
    2. Labeling of Proteins in vitro (P9302)