Recombinant streptavidin from Streptomyces avidinii, produced in E.coli.

Streptavidin is a tetrameric protein that has no carbohydrate and thereby reduces the amount of non specific binding. 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.