TIK, a novel serine/threonine kinase, is recognized by antibodies directed against phosphotyrosine

We have isolated cDNAs encoding kinases from a murine pre-B cell line by screening a lambda gt11 cDNA expression library with anti-phosphotyrosine antibodies. One cDNA was identified to encode the previously isolated tyrosine kinase c-lyn. Among the remaining clones, we have characterized a cDNA encoding a novel kinase which we have designated TIK. Sequence analysis of this cDNA indicates that the TIK enzyme lacks the features thought to be conserved among protein tyrosine kinases. Although isolated on the basis of its reactivity with the anti-phosphotyrosine antibody, the TIK enzyme was found to have only serine and threonine kinase activity. The amino-terminal portion of the TIK protein contains a cdc2 phosphorylation consensus sequence. Three mRNA transcripts derived from the TIK gene are detected in a variety of adult murine tissues.