A substrate peptide for the FLT3 receptor tyrosine kinase.

FLT3 (fms-like tyrosine kinase 3) is frequently activated by mutation in acute myeloid leukemia, and is therefore under study as a drug target. Testing and characterization of tyrosine kinase inhibitors is facilitated by the availability of efficient peptide substrates. Searching for FLT3 peptide substrates using phosphorylation experiments on peptide arrays and in solution revealed that the peptide F-T-D-R-L-Q-Q-Y(8)-I-S-T-R-G-L-G is efficiently phosphorylated (apparent Km 10 micromol/l), with Y8 as the phosphorylated site. This peptide presents a novel tool for identifying and characterizing FLT3 kinase inhibitors.