Identification and characterization of a cytosolic protein tyrosine kinase of HeLa cells.
Fractionation of a cytosolic extract of HeLa cells revealed the existence of a highly active protein tyrosine kinase. Chromatographic fractionation of the extract resulted in partial purification of a single enzymatic activity that coeluted with a 94-kDa polypeptide. In vitro phosphorylation of the isolated enzyme showed that p94 was the only polypeptide phosphorylated and only the tyrosine residue(s) was (were) modified. The fractionated enzyme (p94 kinase) also phosphorylated a number of other nonspecific substrates exclusively on tyrosine residues. Unlike other protein tyrosine kinases that have been characterized, p94 kinase is relatively insensitive to inhibition by the isoflavone genistein. Using two different antisera, we provided evidence that the HeLa p94 kinase is most likely the FER gene product, which was previously shown to be expressed in a wide variety of cell types. These results represent the first biochemical characterization of the cellular FER gene product and also provide a basis for studying the biochemistry of tyrosine kinase function in HeLa cells.
Feller
S M
SM
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
Wong
T W
TW
D000595:Amino Acid Sequence; D000818:Animals; D000936:Antigen-Antibody Complex / Q000737:chemistry; D003600:Cytosol / Q000201:enzymology*; D006367:HeLa Cells / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification; D011817:Rabbits; D013379:Substrate Specificity
D000936:Antigen-Antibody Complex; D011505:Protein-Tyrosine Kinases