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Strep-tag® technology for cell isolation

Besides the well-known tools for protein purification and analyses, the Strep-tag® technology also offers methods for cell staining and isolation. The two main approaches are:

 Direct staining and/or isolation of cells that express a surface protein fused to Strep-tag®II or Twin-Strep-tag®.

Indirect staining and/or isolation via a protein that is fused to Strep-tag®II or Twin-Strep-tag®, which binds to e.g. a specific receptor on the cell surface.

For both ways of selecting cells, different available Strep-Tactin® and Strep-Tactin®XT conjugates offer three basic methods for purifying cells out of mixed samples: Affinity chromatography, magnetic cell isolation or fluorescence activated cell sorting (FACS).

Different conjugates for cell selection

Strep-tag cell isolation approaches with agarose, magnetic beads and fluorophore

Due to the various available conjugates, the Strep-tag® technology provides a highly flexible and individually adaptable platform not only for proteins, but also for larger molecules such as cells.

Direct staining and/or isolation of cells

The Strep-tag® technology is a popular system for purifying proteins due to the specific tag-ligand interaction. The same technology also works for proteins that are present on the cell surface. Fusing the Strep-tag®II or Twin-Strep-tag® to a surface protein of choice helps to select a specific cell of interest. Since proteins and cells differ in various characteristics such as size, the properties of used reagents should fit to the chosen target. The Strep-tag® system not only offers products specialized for proteins, but also for cell-based research.

Indirect staining and/or isolation of cells

Fusing the Strep-tag®II or Twin-Strep-tag® to a cell surface molecule for subsequent selection is not always feasible or suitable for a target of interest. Another option to purify a cell population is to utilize a protein that binds to e.g. a receptor on the surface. This is frequently done with e.g. antibodies that are directly or indirectly linked to a fluorophore or a magnetic bead.

The Strep-tag® technology enables the use of any type of protein for cell isolation. This can be an antibody, an antigen, a peptide-loaded MHC class I molecule or another cell-binding protein. As long as the protein of choice is fused to Strep-Tag®II or Twin-Strep-tag®, it can be combined with the available Strep-Tactin®/ Strep-Tactin®XT conjugates to build reagents suitable for cell selection.

The different Strep-Tactin®/ Strep-Tactin®XT conjugates allow the choice for a cell isolation method that is most suitable for a given approach. Fluorescent conjugates permit the staining and sorting of small cell populations via flow cytometry. Strep-Tactin® Magnetic Microbeads are freely scalable when cells are separated via a magnet. For a high number of target cells (>1 x 10^7 cells), Strep-Tactin® TACS Agarose columns are the cost-effective choice.

A great advantage of the available conjugates is their ability to multimerize strep-tagged proteins. This way, even low affinity targets that do not stably bind as monomers can be used to effectively capture cells.

Cell isolation with low affinity Fab fragments using different Strep-Tactin® conjugates
A multimerization of Fab-Streps is required to increase the avidity sufficiently to immobilize target cells

Even low affinity Fab fragments can be used for effective cell isolation. The different Strep-Tactin® conjugates increase the avidity sufficiently to allow stable binding to cells. 

Removal of Strep-Tactin® and Strep-Tactin®XT conjugates

Independent from the chosen cell selection method, Strep-Tactin® and Strep-Tactin®XT conjugates can easily be removed from the cell surface by biotin addition. Due to its affinity to Strep-Tactin® and Strep-Tactin®XT, it will release any strep-tagged molecule from the used conjugate. This way, cells can be used for further downstream applications such as cell culture without being affected by attached selection reagents.

Find out more about Strep-tag® cell isolation

Here, we have grouped links to make it easier to find more information about Strep-tag® technology for cell isolation. Find the products that fit your research needs. Have a look at the frequently asked questions about the use of Strep-tag® for cell isolation and references. Find application notes, brochures and flyers in our download area and browse through the application examples.