Phosphorylation of tyrosine residues of calmodulin in Rous sarcoma virus-transformed cells.
Calmodulin, a wide-spread eukaryotic Ca2+-binding protein, was phosphorylated at its tyrosine residues in Rous sarcoma virus (RSV)-transformed chicken and rat cells but not in normal chicken embryo fibroblasts. In contrast, serine and threonine phosphorylation of calmodulin was found to occur in both normal and virus-transformed cells. In an in vitro system containing purified src kinase from RSV-transformed cells, tyrosine phosphorylation of calmodulin by the src kinase was inhibited by Ca2+. Furthermore, the tyrosine-phosphorylated calmodulin showed slower mobility than that of nonphosphorylated calmodulin in NaDodSO4/polyacrylamide gel electrophoresis when Ca2+ was present. These results suggest that the structure of calmodulin Ca2+ complex may be altered by tyrosine phosphorylation. It is thus inferred that Ca2+ may regulate the level of tyrosine phosphorylation of calmodulin in RSV-transformed cells, and phosphorylation in turn may attenuate the function of this protein in vivo.
D000818:Animals; D001358:Avian Sarcoma Viruses; D002147:Calmodulin / Q000378:metabolism*; D002472:Cell Transformation, Viral; D002642:Chick Embryo; D066298:In Vitro Techniques; D015688:Oncogene Protein pp60(v-src); D010766:Phosphorylation; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012191:Retroviridae Proteins / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D002147:Calmodulin; D012191:Retroviridae Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src)