STRUCTURE, EXPRESSION AND CHROMOSOMAL MAPPING OF TKT FROM MAN AND MOUSE - A NEW SUBCLASS OF RECEPTOR TYROSINE KINASES WITH A FACTOR VIII-LIKE DOMAIN

Using a polymerase chain reaction-mediated approach we have characteri zed cDNAs from human and mouse origin representing a novel type of rec eptor protein tyrosine kinase (RTK). The deduced amino acid sequence ( 855 amino acids) of the Longest open reading frame has a unique extrac ellular region encompassing a factor VIII-like domain, not previously described for RTKs. The most closely related RTKs are members of the n eurotrophin receptors (TRK), which showed 47-49% homology with the kin ase domain of the new RTK. Therefore, the new gene has been called TKT (Tyrosine-Kinase related to TRK). TKT orthologs from man and mouse we re 98% similar. In both species a major transcript of 10 kb was found to be expressed at high levels in heart and lung. Low levels of this m RNA-species were detected in human brain, placenta, liver, skeletal mu scle, kidney and in mouse brain and testis. Analysing human/mouse soma tic cell hybrids we demonstrated that TKT segregates with human chromo some 1.