Streptavidin

Streptavidin is a tetrameric protein composed of identic subunits. Each subunit binds one biotin molecule with a high degree of affinity and specificity with KD of ~1x10-15 M which makes it one of the strongest known non-covalent interaction. The preparation contains an N- and C-terminal shortened variant (core streptavidin) with improved properties concerning homogenity, solubility, resistance towards proteolytic degradation and accessibility of the biotin binding pocket as compared to native streptavidin.