Tyrosine-protein kinase HCK is a protein-tyrosine kinase that is predominantly expressed in hemopoietic cell types. The encoded protein may help couple the Fc receptor to the activation of the respiratory burst. In addition, it may play a role in neutrophil migration and in the degranulation of neutrophils. Alternate translation initiation site usage, including a non-AUG (CUG) codon, results in the production of two different isoforms, that have different subcellular localization.HCK, the deduced amino acid sequence of the protein encoded by HCK, and the distribution of RNA transcribed from HCK among various hemopoietic cells.Since this region is affected by interstitial deletions in some acute myeloid leukemias and myeloproliferative disorders, they suggested that damage to HCK may contribute to the pathogenesis of these conditions.