Tyrosine kinase (PTKs) is a protein that carries out tyrosine phosphorylation, which play a fundamental role in cell proliferation, survival, adhesion, and motility and have also been demonstrated to mediate malignant cell transformation. Overexpression of this protein in mammary epithelial cells leads to sensitization of the cells to epidermal growth factor and results in a partially transformed phenotype. Two classes of PTKs are present in cells: the transmembrane receptor PTKs and the non-receptor PTKs. Tyrosine kinase(PTKs)-6/ BRK is a cytoplasmic non-receptor protein kinase that may function as an intracellular signal transducer in epithelial tissues. Tyrosine kinase(PTKs)-6/ BRK has been shown to undergo autophosphorylation. It has been found that the constitutive expression of the tyrosine kinase(PTKs)-6/ BRK is in a large proportion of cutaneous T-cell lymphomas and other transformed T- and B-cell populations. State BRK expression was also induced in normal T-cells. In clinical, the cytoplasmic tyrosine kinase PTK6 (BRK) shows elevated expression in approximately two-thirds of primary breast tumours, and is implicated in EGF receptor-dependent signalling and epithelial tumorigenesis.

> 89 % as determined by SDS-PAGE