STREPTAVIDIN-AP CONJUGATE

Streptavidin-AP conjugate is a recombinant protein purified from E. coli. It is supplied as a purified product conjugated to the enzyme alkaline phosphatase (AP). This reagent may be used as a detection reagent for biotin conjugated primary antibodies in immunoassay applications.

PRODUCT INFORMATION – STREPTAVIDIN-AP CONJUGATE

• Recombinant streptavidin expressed in E. coli.
• Conjugated to alkaline phosphatase (AP).
• For use in ELISA, FLISA, FC, WB.

BACKGROUND

Streptavidin is a 52.8 kDa protein (tetramer) purified from the bacterium Streptomyces avidinii, with an extremely high affinity and specificity for biotin (also known as vitamin B7 or vitamin H) (Green, 1975). The biological function of streptavidin is not known. However, the streptavidin-biotin complex shows high resistance to organic solvents, denaturants (e.g. guanidinium chloride), detergents (e.g. SDS, Triton), proteolytic enzymes, and extremes of temperature and pH. As such it is very useful tool for purification and/or detection of biomolecules. By attaching the streptavidin protein to a moiety such as a fluorophore or an enzyme. Streptavidin conjugated to fluorophores or enzymes are often used as secondary labeling reagents to detect biotinylated molecules in common research applications, including immunofluorescence microscopy, ELISA, in situ hybridization, immunohistochemistry, microarrays, flow cytometry, western blot, and other applications. Since multiple biotin molecules are available for binding on each primary antibody, streptavidin can amplify enzymatic signals for use in immunohistochemistry (IHC) and microscopy. Different dyes used include Peridinin Chlorophyll Protein Complex (PerCP), Allophycocyanine (APC) und R-Phycoerythrin (RPE), Alexa Fluor®- und cyanin-conjugated streptavidin and fluorophores such as Fluorescein isothiocyanate (FITC). Streptavidin can also be conjugated to enzymes such as Horseradish Peroxidase (HRP) and Alkaline Phosphatase (AP) for indirect immunodetection. Biotin can also be conjugated to streptavidin for use in IHC. Avidin, originally isolated from egg yolk, also has a very high binding affinity to biotin. It only has 30% sequence identity to streptavidin, but almost identical secondary, tertiary and quaternary structure. However, avidin has a lower binding affinity than streptavidin when biotin is conjugated to another molecule, despite avidin having the higher affinity for free, unconjugated biotin.

REFERENCES

• Green NM (1975). Avidin. Advances in Protein Chemistry. 29: 85–133.