Phosphorylation and regulatory effects of the carboxy terminus of a Drosophila src homolog.
The kinase activities of the vertebrate src family members are repressed by phosphorylation of a tyrosine residue in the carboxy-terminal 'tail' of these molecules. To explore whether the tail of an invertebrate src homolog might also serve a regulatory function, we examined the ability of the carboxy terminus of a Drosophila src homolog (p62D), which contains a tyrosine homologous to those in the vertebrate src family members, to regulate the following molecules in mammalian fibroblasts: (1) a chimeric protein, p60CD, containing the amino terminus and catalytic domains of chicken p60c-src joined to the C-terminus of p62D; and (2) full-length p62D itself. By a variety of criteria p60CD appears to be a partially, rather than fully, repressed form of p60c-src. Phosphopeptide mapping indicates that partial repression correlates with partial phosphorylation of the tyrosine in the p62D tail of the chimera. Phosphorylation of the tail may also regulate full-length p62D. Expression of p62D in fibroblasts does not affect cell morphology or the overall abundance of tyrosine-phosphorylated proteins. The molecule is phosphorylated at its C-terminal tyrosine (Tyr-547), but not at its in vitro autophosphorylation sites, suggesting that it is catalytically repressed in fibroblasts. Expression of a truncated p62D mutant lacking Tyr-547 is associated with a clear alteration in cellular morphology and a two- to threefold increase in cellular phosphotyrosine levels. These results suggest that phosphorylation of the C-terminal tyrosine of the tail of an invertebrate src-like kinase can repress the activity of adjacent catalytic domains.
Kussick
S J
SJ
Department of Pathology, University of Washington School of Medicine, Seattle 98104.
Cooper
J A
JA
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D003001:Cloning, Molecular; D004330:Drosophila / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins; D008969:Molecular Sequence Data; D015688:Oncogene Protein pp60(v-src) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010449:Peptide Mapping; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid
D029721:Drosophila Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D011505:Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src); C075699:Src64B protein, Drosophila