G-Biosciences' recombinant streptavidin comes from streptomyces avidinii, produced in E.coli

• Specific activity >17 U/mg protein (1U binds 1 µg D-biotin at a pH of 8.9)

Streptavidin is a tetrameric protein that has no carbohydrate modifications. The solubility of streptavidin (isoelectric pH 5) in aqueous buffer is lower than avidin, but the binding of streptavidin to biotin is similar to that of avidin. The advantage of streptavidin is that the lack of carbohydrates significantly reduces the amount of non-specific binding.

G-Biosciences' recombinant streptavidin is supplied as white lyophilizate, lyophilized in 20 mM potassium phosphate at a pH of 6.5. Its pH stability ranges from 5.0 to 9.0; its water solubility is 10 mg/mL; its isoelectric point ranges from 6.8 to 7.5; and its molecular weight is approximately 52,000 Da. G-Biosciences' streptavidin is also available immobilized on agarose or coated on 96-well plates.

Biotin, a 244Da vitamin (Vitamin H) molecule, exhibits an extraordinary binding affinity for streptavidin (Ka=10¹⁵M⁻¹). Biotin and streptavidin interaction is rapid. Once the bond is established, it can survive up to 3M guanidine-hydrochloride and extreme levels of pH. Biotin-streptavidin bonds can only be reversed by denaturing the streptavidin protein molecule with 8M guanidine-hydrochloride at a pH of 1.5, or by autoclaving.