title: Regulation of rat cardiac nuclei-associated Mg(2+)-NTPase by phosphorylation.
abstract: A nucleoside triphosphatase (NTPase) activity appeared to be associated with a highly purified nuclear preparation from rat cardiac ventricles. Different nucleoside triphosphates (UTP greater than GTP greater than ITP greater than CTP) supported this enzymic activity, which was stimulated by Mg2+ but not by Ca2+. The nuclear NTPase activity could be down regulated by endogenous phosphorylation of a 55,000 Mr protein. Maximal phosphorylation of the 55,000 Mr protein occurred in the presence of Mg(2+)-ATP. Addition of cAMP, cGMP, Ca2+, Ca2+/phospholipid, Ca2+/calmodulin, and catalytic subunit of cAMP-dependent protein kinase was not associated with any further phosphorylation of the 55,000 Mr protein. However, in the presence of Ca2+/calmodulin or the catalytic subunit of the cAMP-dependent protein kinase additional proteins became phosphorylated, but these had no effect on the Mg(2+)-NTPase activity. These results indicate that a protein with Mr 55,000 may be involved in the regulation the Mg(2+)-NTPase activity associated with rat cardiac nuclei.
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio.
authors.forename: R C
authors.initials: RC
authors.lastname: Gupta
authors.forename: E F
authors.initials: EF
authors.lastname: Young
authors.forename: D G
authors.initials: DG
authors.lastname: Ferguson
authors.forename: E G
authors.initials: EG
authors.lastname: Kranias
mesh_terms: D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002467:Cell Nucleus / Q000201:enzymology*; D004789:Enzyme Activation; D007425:Intracellular Membranes / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D043583:Nucleoside-Triphosphatase; D010750:Phosphoproteins / Q000502:physiology*; D010744:Phosphoric Monoester Hydrolases / Q000302:isolation & purification* / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D008565:Membrane Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D010744:Phosphoric Monoester Hydrolases; D017301:Ca(2+) Mg(2+)-ATPase; D043583:Nucleoside-Triphosphatase; D008274:Magnesium; D002118:Calcium