Human LTK Antibody

LTK (Leukocyte tyrosine kinase; also protein tyrosine kinase 1) is a glycoprotein member of the tyrosine protein kinase family, insulin receptor subfamily of proteins. There are multiple isoforms that run between 50 and 100 kDa in SDS-Page. It is reportedly expressed in lymphocytes and cerebral cortex neurons, plus cardiomyocytes where it plays a role in cellular hypertrophy. Mature human LTK is an 848 amino acid (aa) type I transmembrane protein that is embedded in the ER. It contains a 408 aa extracellular domain (aa 17-424) plus a 415 aa cytoplasmic region (aa 450-864). The cytoplasmic region possesses multiple phosphotyrosines that interact with downstream signaling molecules. There is also a protein kinase domain between aa 510-786. LTK apparently undergoes dimer- and trimerization under certain circumstances. There are multiple splice variants for LTK. Two isoforms possess a common deletion of aa 274-334 that may be accompanied by a 27 aa substitution for aa 449-544. Another isoform shows an alternative start site at Met406 accompanied by a 17 aa substitution for Val449, while a fourth isoform contains a 51 aa substitution for aa 171-864. A final 50 kDa isoform shows a 28 aa substitution for aa 449-864. Over aa 17-424, human LTK shares 75% aa identity with mouse LTK.