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Protein Purification - Application Examples for Strep-Tactin®XT

New applications of the 3rd generation Strep-tag® system

Strep-Tactin®XT:Twin-Strep-tag® is the most versatile affinity purification system and can be used for all kind of applications:
Batch purification

For batch purification IBA provides Strep-Tactin®XT coated magnetic beads: MagStrep "type3" XT beads. MagStrep "type3" XT beads allow the batch purification of highly pure proteins in Strep-tag® quality and the possibility of different elution procedures:

  • Native conditions using biotin
  • Denaturing conditions using sample buffer and boiling for elution
For more information about our MagStrep "type 3" beads click here.
Download Flyer:

For quick and dirty test purification in batch format you can also use Strep-Tactin®XT Superflow® resin.

Example purification


Purification of GFP-Strep-tag fusion protein from crude bact. extract using MagStrep “type3” XT beads

Due to specific binding properties of the beads even the elution by boiling leads to highly pure proteins (GFP peak at ~28kDa ignoring Strep-Tactin XT peak).
(Protein purification analysis was performed with an Agilent Bioanalyzer 2100 system instead of SDS-PAGE)
Purification under denaturing conditions

The expression of recombinant proteins, especially using bacterial vectors and hosts, is a mature and powerful technology and allows the production of a desired protein in large quantities. The procedure to obtain a recombinant protein is straightforward. The gene of interest is cloned into the appropriate expression vector, transformed in the host of choice, induced and then the expressed protein can be purified. In practice, however, things turn out to be more difficult.

One problem is, of course, how to isolate it in an active form.

Soluble proteins can be recovered with good yields (> 50 %), and insoluble proteins, which must undergo a denaturation and folding cycle, can be recovered with more modest yields (5 % to 20 %). [Wingfield, 2016; Rosano and Ceccarelli, 2014]

IBA’s newly developed Strep-Tactin®XT with its near covalent binding affinity for Twin-Strep-tag® (and improved binding affinity for Strep-tag®II) enables increased protein yields of insoluble proteins when purified with up to 6 M urea.
The main advantages of the Strep-tag® system compared to His-tag purification are:

  • purification within a single purification step – no additional chromatography step is required
  • protein purity > 95 %

The 3rd generation Strep-tag® system can now be used for purification under denaturing conditions using up to 6 M urea.

Check the application note for a comparison of the 3rd generation Strep-tag® system to His-tag:NiNTA purification under denaturing conditions.

Download experimental data:

Strep-Tactin®XT under denaturing conditions

Download protocol:

Purification with Strep-Tactin®XT under denaturing conditions

High-throughput screening

Recommended products for high-throughput applications:

Purification of integral membrane proteins with Strep-Tactin®XT

The novel high affinity resin Strep-Tactin®XT was sucessfully tested for purification of integral membrane proteins:

Application of Strep-Tactin®XT for affinity purification of Twin-Strep-tagged CB2, a G protein-coupled cannabinoid receptor (Yeliseev et al., 2016)