Easily induce and express phosphorylated proteins, which can be used to screen expression libraries, to affinity purify or blot proteins that interact with the tyrosine-phosphorylated target.

• Competent cell lines for inducible phosphoprotein expression

TKB1 Competent Cells are derived from the BL21 strain and are intended for use with pET, pCAL or other T7 RNA promoter-based vectors. TKX1 Competent Cells are derived from the XL1-Blue strain and are intended for use with non-T7 promoter-based vectors.

The BL21(DE3) TK strain, abbreviated TKB1, carries the gene for T7 RNA polymerase in the chromosome under the control of the lacUV5 promoter. Induction of the polymerase with isopropyl-β-D-thio-galactopyranoside (IPTG) allows controlled protein expression of genes placed downstream of the T7 RNA polymerase binding site. The TKB1 strain harbors a plasmid encoded,inducible tyrosine kinase gene (pTK).

TKX1 competent cells are a tyrosine kinase (TK) derivative of the XL1-Blue MRF´ Kan strain. TKX1 competent cells are resistant to kanamycin. The XL1-Blue MRF´ Kan TK strain, abbreviated TKX1, harbors a plasmid encoded, inducible tyrosine kinase gene (pTK).

The TKB1 and TKX1 strain can be transformed with a plasmid (ColE1 origin) containing a DNA sequence encoding a phosphorylation target domain or protein. If the target protein is cloned as a fusion to an affinity tag, purification of large amounts of phosphorylated protein is relatively easy. The phosphorylated protein isolated from the TK strain can be used to screen expression libraries and to affinity purify or blot proteins that interact with the tyrosine-phosphorylated target.