title: Zn(2+)-dependent tyrosine phosphorylation of a 68-kDa protein and its differentiation from Mg(2+)-dependent tyrosine phosphorylation in sheep platelets.
abstract: A 68-kDa protein that was tyrosine phosphorylated in the presence of Zn2+ and two proteins of 52 and 46 kDa that were tyrosine phosphorylated in the presence of Mg2+ were separated by column chromatography of a sheep platelet high speed supernatant on poly(Glu, Tyr)4:1 copolymer-Sepharose or tyrosine-Sepharose. Phosphorylation of the 68-kDa protein occurred maximally in the presence of Zn2+ while Mg2+ was ineffective. The kinases responsible for the Zn(2+)- and Mg(2+)-dependent tyrosine phosphorylation could also tyrosine phosphorylate poly(Glu, Tyr)4:1, histone, and angiotensin II with the same metal ion specificity. The two tyrosine kinase activities could be also distinguished by their differential response to polyamines and quercetin. Zn2+ stimulation did not appear to be due to the inhibition of a protein tyrosine phosphatase. Sephadex G-100 gel filtration of the fraction showing Zn(2+)-dependent tyrosine phosphorylation of the 68-kDa protein showed that the tyrosine kinase activity corresponded to a molecular mass of 68,000 and it showed a protein band of 68 kDa as detected by silver staining on sodium dodecyl sulfate-polyacrylamide gel.
authors.affiliation: Department of Neurological Sciences, Christian Medical College Hospital, Vellore, India.
authors.forename: S
authors.initials: S
authors.lastname: Ramamoorthy
authors.forename: A S
authors.initials: AS
authors.lastname: Balasubramanian
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001798:Blood Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D010766:Phosphorylation; D019000:Phosphotyrosine; D011073:Polyamines / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000097:blood*; D011794:Quercetin / Q000494:pharmacology; D012756:Sheep; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis; D015032:Zinc / Q000494:pharmacology*
chemical_list: D001798:Blood Proteins; D011073:Polyamines; D019000:Phosphotyrosine; D014443:Tyrosine; D011794:Quercetin; D011505:Protein-Tyrosine Kinases; D008274:Magnesium; D015032:Zinc