This peptide sequence exhibits intrinsic affinity towards Strep-Tactin, a specifically engineered streptavidin, and can be N- or C- terminally fused to recombinant proteins.
By exploiting the highly specific interaction, Strep-tagged proteins can be isolated in one step from crude cell lysates.
The Strep-tag was originally selected from a genetic library to specifically bind to a proteolytically truncated "core" version of streptavidin.
[3] Just like other short-affinity tags (His-tag, FLAG-tag), the Strep-tag can be easily fused to recombinant proteins during subcloning of its cDNA or gene.
Then, the purified Strep-tag fusion protein is gently eluted with a low concentration of desthiobiotin, which specifically competes for the biotin binding pocket (step 3).
Another option is the immobilization of Strep-tag proteins with a specific high affinity antibody on microplates or biochips.
Strep-Tag/StrepTactin system is also used in single-molecule optical tweezers and atomic force microscope experiments, showing high mechanical stability comparable to the strongest non-covalent linkages currently available.