The Strep-tag system is based on the highly selective and easily controllable interaction between the Strep-tag II peptide and the specially engineered streptavidin called Strep-Tactin.
The binding affinity of Strep-tag II to Strep-Tactin is nearly 100 times higher than to Streptavidin. The short peptide tag (8 amino acids) has negligible effect on the recombinant protein due to its chemically balanced amino acid composition (WSHPQFEK). The tag can be placed at the C- or N-terminus. A two amino acid spacer between the protein and the tag is recommended to ensure accessibility of the tag. Generally, it does not interfere with folding or bioactivity, does not react with heavy metal ion buffer impurities, has no ion exchange properties and does not induce protein aggregation.
Attractive offers for newcomers are IBA's Strep-tag Starter Kits containing all essential reagents required for expression in E. coli, purification and detection of Strep-tag proteins. For the appropriate expression vector of choice we offer discounts if purchased in combination with a Starter Kit.
The Strep-tag Starter Kit is sufficient for 8 applications:
1 ready-to-use column with Strep-Tactin Sepharose,
1 ml, gravity flow Control plasmid with 15 kD protein insert,
Anhydrotetracycline for induction of expression,
Fractionation buffer for the preparation of a periplasmic extract,
Washing buffer for column chromatography or for the preparation of a cytoplasmic extract,
Elution buffer for displacing the Strep-tag protein from the column,
Column regeneration buffer (with HABA),
Strep-Tactin horse radish peroxidase (HRP) conjugate for Western blot detection,