Schematic diagram of the NPM-ALK fusion protein. As a result of the 2; 5 translocation, the amino-terminal portion of NPM is fused to the intracellular region (including the tyrosine kinase domain) of ALK. The recombinant protein used to raise the MoAb ALK1 consists of the portion of ALK between amino acids 419 and 520, inclusive. MB indicates putative metal binding site.