title: Restoration of phosphorylation capacity to the dormant half of the alpha-subunits of Na+, K(+)-ATPase.
abstract: Purified kidney Na+, K(+)-ATPase whose alpha-subunit is cleaved by chymotrypsin at Leu266-Ala267, loses ATPase activity but forms the phosphoenzyme intermediate (EP) from ATP. When EP formation was correlated with extent of alpha-cleavage in the course of proteolysis, total EP increased with time before it declined. The magnitude of this rise indicated doubling of the number of phosphorylation sites after cleavage. Together with previous findings, these data establish that half of the alpha-subunits of oligomeric membrane-bound enzyme are dormant and that interaction of the N-terminal domain of alpha-subunit with its phosphorylation domain causes this half-site reactivity. Evidently, disruption of this interaction by proteolysis abolishes overall activity while it opens access to phosphorylation sites of all alpha-subunits.
authors.affiliation: Department of Pharmacology, Medical College of Ohio, Toledo 43699-0008, USA.
authors.forename: G
authors.initials: G
authors.lastname: Liu
authors.forename: Z
authors.initials: Z
authors.lastname: Xie
authors.forename: N N
authors.initials: NN
authors.lastname: Modyanov
authors.forename: A
authors.initials: A
authors.lastname: Askari
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002918:Chymotrypsin / Q000378:metabolism; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007679:Kidney Medulla / Q000201:enzymology*; D007700:Kinetics; D010766:Phosphorylation; D011487:Protein Conformation; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D000255:Adenosine Triphosphate; D002918:Chymotrypsin; D000254:Sodium-Potassium-Exchanging ATPase