Avidin (Biotin-binding protein) (AVD)

Biotin-binding proteins, most notably Avidin (from avian egg whites) and Streptavidin (from the bacterium Streptomyces avidinii), are tetrameric proteins characterized by their extraordinarily high affinity for the vitamin D-biotin (Vitamin B7). This interaction is one of the strongest known non-covalent biological bonds (Kd ≈ 10^-15 M), characterized by a highly specific binding pocket that undergoes conformational changes to lock the biotin molecule in place. While their natural biological role is primarily antimicrobial—depleting biotin to inhibit the growth of biotin-dependent microorganisms—they have become indispensable tools in biotechnology and pharmacology. In therapeutic contexts, they are utilized in 'pre-targeting' strategies, where a biotinylated or streptavidin-conjugated antibody is first localized to a tumor, followed by the administration of a radiolabeled or cytotoxic partner. This allows for high-precision drug delivery and signal amplification in both diagnostics and cancer therapy.

Other names

AvidinStreptavidinBBPNeutravidinBiotin-binding protein ABiotin-binding protein IBiotin-binding protein II

High-affinity non-covalent sequestration of biotinylated payloads; pre-targeted tumor localization; signal amplification in diagnostic assays.