Streptavidin vs. Avidin

Streptavidinnoun

(protein) A tetrameric protein purified from Streptomyces avidinii that binds very tightly to the vitamin biotin

Avidinnoun

(biology) A tetrameric protein produced in the oviducts of birds, reptiles and amphibians and deposited in the whites of their eggs.

Streptavidin

Streptavidin is a 66.0 (tetramer) kDa protein purified from the bacterium Streptomyces avidinii. Streptavidin homo-tetramers have an extraordinarily high affinity for biotin (also known as vitamin B7 or vitamin H).

Avidin

Avidin is a tetrameric biotin-binding protein produced in the oviducts of birds, reptiles and amphibians and deposited in the whites of their eggs. Dimeric members of the avidin family are also found in some bacteria.