FRK (fyn-related kinase) or Rak is a nuclear tyrosine kinase and member of the Src sub-family. Restricted expression of FRK is detected in a broad range of cell lines with highest levels in epithelial cells. Increased expression of FRK has been shown in breast and renal cell carcinoma cell lines. In addition the retinoblastoma tumor susceptibility gene product pRb associates with FRK in vitro and in vivo (1). Overexpression of FRK in β-cells from the pancreas increases the susceptibility of these cells to β-cell-toxic events (hallmark of Type I diabetes)(2). MW: 60.0 kDa. Purity ≥90%