Biotinylated Proteins: Better insight through better binding

The bond between Biotin and Streptavidin is one of the strongest non-covalent bonds ever identified. It is frequently exploited in molecular biology to couple two different molecules that would not traditionally bind each other.

What is biotin?

Biotin is a small molecule (~244 Da) produced by living organisms. Also known as Vitamn B₇, biotin acts as a coenzyme, and is necessary for the synthesis of various physiologically relevant compounds.

What is avidin/streptavidin?

Avidin and streptavidin are both tetrameric proteins that possess an exceptionally high affinity for biotin. Avidin is naturally found in egg-whites, and in the oviducts of a variety of egg producing animals, while streptavidin is produced by Streptomyces avidinii. Curiously, while these two structures share little sequence similarity, they produce very similar higher-order structures. Both are thought to have evolved as a method of inhibiting bacterial growth (a number of bacterial species rely upon biotin for critical metabolic processes).

Why use biotin/streptavidin?

In molecular biology and biotechnology, biotin is widely utilized as conjugate for antibodies or other proteins. The relatively small size of biotin means that it can be safely conjugated to many complex, folded protein structures without the concern that stearic inhibition will interfere with production, folding, or physiological function of the host protein.

The interaction between biotin and streptavidin is among the strongest non-covalent chemical bonds ever identified^[1], and biotin-streptavidin is often applied like “molecular velcro” to physically attach two different structures that would typically not interact.

For example, biotin conjugated antibodies are frequently used with a variety of streptavidin conjugated dyes or enzymes. By utilizing this approach, and separating the antibody from its detection conjugate, one develops an exceptionally powerful and versatile tool. Now a single antibody could potentially be used with a streptaividin-conjugated fluorescent dye for cell sorting and IF microscopy, a streptavidin-conjugated peroxidase enzyme for histochemistry or ELISA, and even strepatividin-conjugate gold particles for immune-electron microscopy.

See all biotinylated antibodies

Biotinylated recombinant proteins

Biotin-streptavidin is a core element in modern proteomic analysis. In fact, most ELISA kits make use of biotinylated antibodies, and streptavidin conjugated peroxidase enzymes.

One vital, but often underexplored avenue however is biotinylated recombinant proteins.

By conjugating an active, recombinant protein with biotin, one opens up a world of possibilities for investigating protein-protein interactions, or probing physiological function.

FDA: Biotin May Interfere with Lab Tests

The US Food & Drug Administration (FDA) is a federal agency of the United States Department of Health and Human Services. According to the safety communication given out by the FDA anually, biotin can significantly interfere with certain lab tests and cause incorrect test results which may go undetected.

Be aware that many lab tests, including but not limited to cardiovascular diagnostic tests and hormone tests, that use biotin technology are potentially affected, and incorrect test results may be generated if there is biotin in the patient’s specimen.

Investigate interference from biotin (up to at least 1200 ng/mL biotin) in your assays that use biotin technology. Determine the lowest concentration of biotin that may cause clinically significant interference with your test(s).

Biotin in blood or other samples taken from patients who are ingesting high levels of biotin in dietary supplements can cause clinically significant incorrect lab test results. The number of reported adverse events is rising, including one death, related to biotin interference with lab tests.

Currently available data is insufficient to support recommendations for safe testing using affected tests in patients taking high levels of biotin, including about the length of time for biotin clearance from the blood.