Streptavidinjärjestelmiä

Streptavidin is a protein secreted by the bacterium Streptomyces avidinii. It is renowned for its exceptionally strong and specific binding affinity for biotin, a vitamin also known as vitamin B7 or vitamin H. This interaction is one of the strongest known non-covalent bonds in biology, with a dissociation constant (Kd) in the femtomolar range.

The streptavidin molecule is a homotetramer, meaning it consists of four identical polypeptide subunits. Each subunit contains a biotin-binding site, allowing a single streptavidin tetramer to bind up to four molecules of biotin simultaneously. This multivalent binding is a key feature that makes streptavidin so useful in various biochemical and biological applications.

The high specificity and affinity of the streptavidin-biotin interaction have led to its widespread use as a detection and purification tool in molecular biology and biotechnology. It is frequently employed in assays such as ELISA (enzyme-linked immunosorbent assay), Western blotting, and immunohistochemistry, where it serves to link a detection molecule (like an enzyme or fluorescent dye) to a target molecule that has been labeled with biotin. Streptavidin also plays a crucial role in affinity chromatography for purifying biotinylated molecules. Its stability under a wide range of conditions, including heat and pH, further enhances its utility in diverse experimental settings.