Streptavidin

Streptavidin
Monomeric streptavidin (ribbon diagram) with bound biotin (spheres); PDB: 1STP​
Identifiers
Organism	Streptomyces avidinii
Symbol	?
UniProt	P22629
Search for Structures Swiss-model Domains InterPro

Streptavidin /ˌstrɛpˈtævɪdɪn/ is a 52 kDa protein (tetramer) purified from the bacterium Streptomyces avidinii. Streptavidin homo-tetramers have an extraordinarily high affinity for biotin (also known as vitamin B7 or vitamin H). With a dissociation constant (K_d) on the order of ≈10⁻¹⁴ mol/L,^[1] the binding of biotin to streptavidin is one of the strongest non-covalent interactions known in nature. Streptavidin is used extensively in molecular biology and bionanotechnology due to the streptavidin-biotin complex's resistance to organic solvents, denaturants (e.g. guanidinium chloride), detergents (e.g. SDS, Triton X-100), proteolytic enzymes, and extremes of temperature and pH.