title: The calcium pump of the liver nuclear membrane is identical to that of endoplasmic reticulum.
abstract: The envelope membrane of rat liver nuclei contains a P-type Ca(2+)-transporting pump, revealed by the presence of a Ca(2+)-stimulated phosphoenzyme. The level of the nuclear phosphoenzyme in autoradiographed polyacrylamide gels was decreased by lanthanum, as typically observed in the endoplasmic reticulum Ca2+ pump. It was also decreased by thapsigargin and 2,5-di-(tert-butyl)-1,4-benzohydroquinone, two accepted inhibitors of the endoplasmic reticulum Ca(2+)-ATPase. Comparative proteolysis of the phosphorylated enzyme of liver microsomes (endoplasmic reticulum) and nuclear membranes revealed an identical cleavage pattern. In addition, antibodies raised against the endoplasmic reticulum Ca2+ pump cross-reacted with the pump in the nuclear membranes. The findings show that nuclear membranes contain a Ca(2+)-transporting pump closely related to that of the endoplasmic reticulum, if not identical to it. The pump is likely to be involved in the control of nuclear free calcium.
authors.affiliation: Institute of Biochemistry, Swiss Federal Institute of Technology (ETH), Zurich.
authors.forename: L
authors.initials: L
authors.lastname: Lanini
authors.forename: O
authors.initials: O
authors.lastname: Bachs
authors.forename: E
authors.initials: E
authors.lastname: Carafoli
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000276:immunology; D002413:Cations, Divalent; D002467:Cell Nucleus / Q000378:metabolism*; D003429:Cross Reactions; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D006868:Hydrolysis; D006873:Hydroquinones / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D051381:Rats; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
chemical_list: D002413:Cations, Divalent; D006873:Hydroquinones; D013729:Terpenes; C019359:2,5-di-tert-butylhydroquinone; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium