Strep-tag®II
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. Thus, there is no need for removing the tag.
Strep-Tactin®
Strep-Tactin is a streptavidin derivative which is one of the most stable proteins known. Streptavidin is stable to treatment with 8 M urea or guanidine, 0.5 M NaOH as well as 50 % formamide (t = 1 h; T = 37 °C). Proteases (proteinase pepsin, papain, subtilisin, thermolysin, elastase) do not cleave streptavidin during a 2 h incubation at a 1:50 w/w ratio and 37 °C. In the presence of SDS streptavidin begins to break up into monomers only at temperatures above 60 °C. As far as tested, we have been able to confirm these extraordinary properties for Strep-Tactin, thus enabling long-lasting affinity columns which can be re-used 3-5 times. Furthermore, the neutral pI of Strep-Tactin minimizes non-specific protein or nucleic acid binding. See also "reagents compatible with Strep-tag / Strep-Tactin interaction".
Benefits
- Purification of bioactive recombinant proteins
- Physiological purification using desthiobiotin elution
- Protein aggregation is avoided
- Broad range of detergents, chelators, salt or redox conditions allowed
- Avoids interaction with heavy metal ions which are toxic and may catalyze protein oxidation
Recommended paper:
For reference of Strep-tag technology please quote "Schmidt TGM and Skerra A, 2007. The Strep-tag system for one-step purification and high-affinity detection or capturing of proteins. NATURE PROTOCOLS 2, 1528-1535."
 abstract
Reprints are available from the authors upon request.
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