Antipeptide antiserum identifies a widely distributed cellular tyrosine kinase related to but distinct from the c-fps/fes-encoded protein.

We raised antibodies directed against a synthetic peptide representing an amino acid sequence of the conserved kinase domain of the transforming protein of Fujinami sarcoma virus (FSV) (P140). The antiserum obtained specifically recognized FSV-P140 and its cellular homolog and in addition, it recognized a new cellular protein of 94,000 daltons (NCP94) in avian and mammalian cells. NCP94 was found to be associated with a cyclic nucleotide-independent protein kinase activity that was specific for tyrosine residues. Although NCP94 and FSV-P140 share antigenic determinants, NCP94 is not a cellular homolog of FSV-P140: NCP94 and the previously identified c-fps/fes product were different in their tryptic fingerprints and in their tissue specificities. Thus, the function of NCP94 in normal cells is probably different than that of the c-fps/fes product. NCP94 was expressed in every tissue and cell line that was examined. In chickens, NCP94 levels were highest during embryonic development and NCP94 expression was high in gizzard, brain, and spleen throughout embryonic and adult life. The universal expression of NCP94 suggests that this protein may be involved in an essential function of normal cells. NCP94 may be a new cellular tyrosine kinase of the src gene family.