Strep-tag II Recombinant Mouse mAb (S-5312)

Strep-tag II is a small peptide affinity tag consisting of eight amino acids with the sequence Trp-Ser-His-Pro-Gln-Phe-Glu-Lys (WSHPQFEK) and a molecular weight of approximately 1.06 kDa. It can be flexibly fused to either the N- or C-terminus of recombinant proteins for affinity purification, detection, immobilization, and protein interaction studies. Strep-tag II specifically binds to the engineered streptavidin derivative Strep-Tactin, in which mutations stabilize a flexible loop near the binding pocket into an "open" conformation, increasing the binding affinity for Strep-tag II nearly 100-fold compared to native streptavidin, with a dissociation constant of approximately 1 μM. The tag itself is biochemically inert and protease-resistant, and typically does not interfere with protein folding, secretion, or function. It can be used under physiological buffer conditions, as well as in the presence of high salt, reducing agents, or mild detergents, making it particularly suitable for one-step purification of fusion proteins with native activity from bacterial, yeast, insect, and mammalian cell lysates. Bound proteins can be competitively eluted using low concentrations of desthiobiotin or biotin under mild conditions, which helps preserve protein activity and allows the chromatography resin to be reused.