Streptavidin

Streptavidin is a protein produced by Streptomyces avidinii and isolated by purification from fermentation broth. The pure, homogeneous protein shows predominantly one single band in SDS PAGE. Streptavidin consists of four identical subunits, each bearing an active binding site for biotin. The neutral isoelectric point (pH 5-6) of streptavidin is in the same area where many biological interactions occur and the high affinity of the biotin-streptavidin interaction results in a very quick reaction with a high signal-to-noise Ratio.
Streptavidin is useful in combination with, for instance, biotinylated antibodies. Other applications cover Southern and Western Blotting, purification done by use of immobilized Streptavidin and methodologies for DNA/RNA analysis. Streptavidin is non-glycosylated and does not react unspecifically with endogenous lectins when used in assays on cells and tissues.