Biotinylated thrombin is useful for cleavage of proteins and peptides at the enzyme recognition sequence Leu-Val-Pro-Arg-||-Gly-Ser. Biotinylated thrombin is then easily removed from the reaction with immobilized avidin agarose resin. This preparation is >95% pure on SDS-PAGE and is tested for activity using thrombin chromogenic substrate and cleavage control protein.

Biotinylated Thrombin Cleavage Protocol
1. Make a 10X cleavage buffer consisting of 0.2M Tris-HCl, 1.5M NaCl, 0.025M CaCl2, pH 8.4.
2. Combine 500ul of 10X cleavage buffer, 1mg of target protein, and 1U of biotinylated thrombin in a total of 5ml.
3. Incubate overnight at room temperature.
4. Remove biotinylated thrombin with immobilized avidin or streptavidin agarose resin according to the manufacturer's recommended directions. This resin cannot be reused.
5. Residual uncleaved fusion tagged protein along with cleaved purification tag in the reaction can usually be removed by reapplying to the original purification resin after reequilibration in binding buffer.

Notes: Optimization of biotinylated thrombin protocol is required for specific applications. Recommended reaction conditions are pH 7.0 to 9.0 at 20C. The reaction rate will be increased by increasing the enzyme to protein substrate ratio and incubation temperature. For example, addition of 2U of biotinylated thrombin and incubation at 37C will result in accelerated thrombin digestion (30-60 minutes).
Cleavage at sites similar to the enzyme recognition sequence can be limited by decreasing enzyme to protein substrate ratio and incubation temperature. A pilot scale digestion is recommended for optimization of the reaction by removing samples at 2, 4, 8, and 16 hours and analyzing by SDS-PAGE.