title: [35S]ATP gamma S binding sites in the purified heart sarcolemma membrane.
abstract: Purified heart sarcolemma membranes were found to bind a slowly hydrolyzable analogue of ATP [35S-labeled adenosine 5'-(gamma-thio)triphosphate [( 35S]ATP gamma S)] in a specific manner and exhibited two apparent affinity sites. The high-affinity site had a dissociation constant (KD) of 4.7-8.3 nM [maximum binding (Bmax) = 9.5-18.4 pmol/mg protein], whereas the low-affinity site had a KD of 655-1,257 nM (Bmax = 812-2,955 pmol/mg protein). Like ATP, other nucleotides such as GTP, UTP, ITP, and CTP were effective in displacing [35S]ATP gamma S binding. Although crude membrane preparations from different tissues also exhibited both high- and low-affinity sites for [35S]ATP gamma S, KD values for the high affinity sites were severalfold higher than that for the purified heart membranes. It is proposed that the high-affinity binding site for nucleotides may represent the ATP receptor in the heart cell membrane.
authors.affiliation: Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
authors.forename: D Y
authors.initials: DY
authors.lastname: Zhao
authors.forename: N S
authors.initials: NS
authors.lastname: Dhalla
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D012265:Ribonucleotides / Q000494:pharmacology; D012508:Sarcolemma / Q000378:metabolism* / Q000648:ultrastructure; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013462:Sulfur Radioisotopes
chemical_list: D012265:Ribonucleotides; D013462:Sulfur Radioisotopes; C022571:adenosine 5'-O-(3-thiotriphosphate); D010042:Ouabain; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase