Streptavidin (SA) is a ~ 60 kDa homologous tetramer protein isolated from the culture medium of Streptomyces avidinii but is now more often recombinantly produced. Like avidin, streptavidin behaves as an antibiotic and binds 4 moles of biotin per mole of protein with a high affinity virtually unmatched in nature (Kd 10-15 mol/L). Due to the lack of the glycoprotein portion in streptavidin and its near-neutral isoelectric point, it exhibits less nonspecific binding than avidin in detection.
Fig. 1 Streptavidin tetramer
Streptavidin Variants by Binding Sites
Monovalent Form: This engineered recombinant variant has only one functional binding site out of four, with a 10-14 mol/L affinity. It is used for applications such as monitoring cell surface receptors and marking areas for cryo-electron microscopy.
Divalent Form: This variant feature two biotin-binding sites per tetramer, created by combining functional and non-functional subunits and purified via ion-exchange chromatography. It is available in two configurations: cis-divalent (close sites) and trans-divalent (distant sites).
Trivalent Form: With three biotin-binding sites per tetramer, this variant is made using a similar approach to the divalent form, offering additional binding capacity for various applications.
Applications of Streptavidin
Streptavidin is widely utilized in the purification and detection of natural and recombinant proteins, as well as other biomolecules. Its strong streptavidin-biotin bond allows for the attachment of these molecules to one another or to a solid surface, which is particularly useful in molecular biology and biotechnology labs.
Streptavidin plays a crucial role in immunoassays such as ELISA and Western blotting, where it is conjugated to reporter molecules like horseradish peroxidase. This enhances the sensitivity of assays and allows for signal amplification, which is essential in detecting biotinylated ligands, antibodies, and DNA probes.
In the field of nanobiotechnology, streptavidin is used to construct nanoscale structures and devices using biological materials like lipids and proteins. It can link biotinylated DNA molecules to form scaffolds for applications such as single-walled carbon nanotubes and complex DNA polyhedra.
Streptavidin affinity grids are employed in cryo-electron microscopy (cryo-EM) sample preparation to overcome challenges such as sample denaturation and preferential orientations. The high-affinity interaction between streptavidin and biotin enables the binding of biotinylated samples, protecting them from the air-water interface during sample preparation.
Streptavidin is also used in DNA origami, a field that involves the construction of DNA nanostructures for applications in bioimaging, bioengineering, and biosensing. These nanostructures can be used as vehicles for controlled drug delivery, leveraging their structural versatility, programmability, and biocompatibility.
Streptavidin is conjugated to monoclonal antibodies that recognize cancer cell-specific antigens in pretargeted immunotherapy. Following the injection of radiolabeled biotin, this approach allows for targeted radiation delivery to malignant cells.
| Cat. No. | Product Name | Source | Application | |
| DAGC789 | Recombinant Streptavidin (pI 7.0) [His] | E. coli | ELISA, IHC | |
| DAGC790 | Recombinant Core Streptavidin (pI 6.04) | E. coli | ELISA, IHC | |
| DAGC791 | Recombinant Core Streptavidin (pI 6.09) | E. coli | ELISA, IHC | |
| DAGC792 | Recombinant Core Streptavidin [HRP] | E. coli | ELISA, WB, IHC | |
| DAGC793 | Recombinant Monomeric Streptavidin (pI 5.68) [His, FLAG] | E. coli | ELISA, IHC | |
| DAGC794 | Recombinant Core Streptavidin (pI 8.93) | E. coli | ELISA, IHC |