Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions

This study examined how the quaternary organic ammonium ion, benzyltriethylamine (BTEA), binds to the Na,K-ATPase to produce membrane potential (VM)-dependent inhibition and tested the prediction that such a VM-dependent inhibitor would display electrogenic binding kinetics. BTEA competitively inhib...

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Publicado:	2009
Materias:	Ammonium ions ATP-ase activity Binding kinetics Binding reactions Extracellular Homology models Initial rate Ion binding Ion transports Membrane potentials Minimum value Pump current Quaternary amines Similar degree Step changes Structural analogue Transient current Transmembrane helices Amines Ammonium compounds Binding energy Binding sites Electric fault currents Enzymes Ions Optical devices Rate constants Ion exchange adenosine triphosphatase (potassium sodium) benzyltriethylamine potassium ion quaternary ammonium derivative rubidium ion unclassified drug amino acid sequence animal cell article binding competition controlled study enzyme activation enzyme binding heart muscle fiber membrane nonhuman patch clamp potassium transport priority journal rat transport kinetics Animals Binding Sites Dogs Electric Conductivity Enzyme Inhibitors Extracellular Space Membrane Potentials Models, Biological Models, Molecular Nitro Compounds Potassium Protein Binding Protein Conformation Quaternary Ammonium Compounds Rabbits Rats Rubidium Sodium-Potassium-Exchanging ATPase Time Factors Strophanthus gratus
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00062960_v48_n34_p8105_Peluffo http://hdl.handle.net/20.500.12110/paper_00062960_v48_n34_p8105_Peluffo
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

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spelling	paper:paper_00062960_v48_n34_p8105_Peluffo2023-06-08T14:30:44Z Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions Ammonium ions ATP-ase activity Binding kinetics Binding reactions Extracellular Homology models Initial rate Ion binding Ion transports Membrane potentials Minimum value Pump current Quaternary amines Similar degree Step changes Structural analogue Transient current Transmembrane helices Amines Ammonium compounds Binding energy Binding sites Electric fault currents Enzymes Ions Optical devices Rate constants Ion exchange adenosine triphosphatase (potassium sodium) benzyltriethylamine potassium ion quaternary ammonium derivative rubidium ion unclassified drug amino acid sequence animal cell article binding competition controlled study enzyme activation enzyme binding heart muscle fiber membrane nonhuman patch clamp potassium transport priority journal rat transport kinetics Animals Binding Sites Dogs Electric Conductivity Enzyme Inhibitors Extracellular Space Membrane Potentials Models, Biological Models, Molecular Nitro Compounds Potassium Protein Binding Protein Conformation Quaternary Ammonium Compounds Rabbits Rats Rubidium Sodium-Potassium-Exchanging ATPase Time Factors Strophanthus gratus This study examined how the quaternary organic ammonium ion, benzyltriethylamine (BTEA), binds to the Na,K-ATPase to produce membrane potential (VM)-dependent inhibition and tested the prediction that such a VM-dependent inhibitor would display electrogenic binding kinetics. BTEA competitively inhibited K+ activation of Na,K-ATPase activity and steady-state 86Rb+ occlusion. The initial rate of 86Rb+ occlusion was decreased by BTEA to a similar degree whether it was added to the enzyme prior to or simultaneously with Rb+, a demonstration that BTEA inhibits the Na,K-ATPase without being occluded. Several BTEA structural analogues reversibly inhibited Na,K-pump current, but none blocked current in a VM-dependent manner except BTEA and its para-nitro derivative, pNBTEA. Under conditions that promoted electroneutral K+-K+ exchange by the Na,K-ATPase, step changes in VM elicited pNBTEA-activated ouabain-sensitive transient currents that had similarities to those produced with the K+ congener, Tl+. pNBTEA- and Tl+-dependent transient currents both displayed saturation of charge moved at extreme negative and positive VM, equivalence of charge moved during and after step changes in VM, and similar apparent valence. The rate constant (ktot) for Tl+-dependent transient current asymptotically approached a minimum value at positive VM. In contrast, k tot for pNBTEA-dependent transient current was a "U"-shaped function of VM with a minimum value near 0 mV. Homology models of the Na,K-ATPase alpha subunit suggested that quaternary amines can bind to two extracellularly accessible sites, one of them located at K+ binding sites positioned between transmembrane helices 4, 5, and 6. Altogether, these data revealed important information about electrogenic ion binding reactions of the Na,K-ATPase that are not directly measurable during ion transport by this enzyme. © 2009 American Chemical Society. 2009 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00062960_v48_n34_p8105_Peluffo http://hdl.handle.net/20.500.12110/paper_00062960_v48_n34_p8105_Peluffo
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Ammonium ions ATP-ase activity Binding kinetics Binding reactions Extracellular Homology models Initial rate Ion binding Ion transports Membrane potentials Minimum value Pump current Quaternary amines Similar degree Step changes Structural analogue Transient current Transmembrane helices Amines Ammonium compounds Binding energy Binding sites Electric fault currents Enzymes Ions Optical devices Rate constants Ion exchange adenosine triphosphatase (potassium sodium) benzyltriethylamine potassium ion quaternary ammonium derivative rubidium ion unclassified drug amino acid sequence animal cell article binding competition controlled study enzyme activation enzyme binding heart muscle fiber membrane nonhuman patch clamp potassium transport priority journal rat transport kinetics Animals Binding Sites Dogs Electric Conductivity Enzyme Inhibitors Extracellular Space Membrane Potentials Models, Biological Models, Molecular Nitro Compounds Potassium Protein Binding Protein Conformation Quaternary Ammonium Compounds Rabbits Rats Rubidium Sodium-Potassium-Exchanging ATPase Time Factors Strophanthus gratus
spellingShingle	Ammonium ions ATP-ase activity Binding kinetics Binding reactions Extracellular Homology models Initial rate Ion binding Ion transports Membrane potentials Minimum value Pump current Quaternary amines Similar degree Step changes Structural analogue Transient current Transmembrane helices Amines Ammonium compounds Binding energy Binding sites Electric fault currents Enzymes Ions Optical devices Rate constants Ion exchange adenosine triphosphatase (potassium sodium) benzyltriethylamine potassium ion quaternary ammonium derivative rubidium ion unclassified drug amino acid sequence animal cell article binding competition controlled study enzyme activation enzyme binding heart muscle fiber membrane nonhuman patch clamp potassium transport priority journal rat transport kinetics Animals Binding Sites Dogs Electric Conductivity Enzyme Inhibitors Extracellular Space Membrane Potentials Models, Biological Models, Molecular Nitro Compounds Potassium Protein Binding Protein Conformation Quaternary Ammonium Compounds Rabbits Rats Rubidium Sodium-Potassium-Exchanging ATPase Time Factors Strophanthus gratus Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions
topic_facet	Ammonium ions ATP-ase activity Binding kinetics Binding reactions Extracellular Homology models Initial rate Ion binding Ion transports Membrane potentials Minimum value Pump current Quaternary amines Similar degree Step changes Structural analogue Transient current Transmembrane helices Amines Ammonium compounds Binding energy Binding sites Electric fault currents Enzymes Ions Optical devices Rate constants Ion exchange adenosine triphosphatase (potassium sodium) benzyltriethylamine potassium ion quaternary ammonium derivative rubidium ion unclassified drug amino acid sequence animal cell article binding competition controlled study enzyme activation enzyme binding heart muscle fiber membrane nonhuman patch clamp potassium transport priority journal rat transport kinetics Animals Binding Sites Dogs Electric Conductivity Enzyme Inhibitors Extracellular Space Membrane Potentials Models, Biological Models, Molecular Nitro Compounds Potassium Protein Binding Protein Conformation Quaternary Ammonium Compounds Rabbits Rats Rubidium Sodium-Potassium-Exchanging ATPase Time Factors Strophanthus gratus
description	This study examined how the quaternary organic ammonium ion, benzyltriethylamine (BTEA), binds to the Na,K-ATPase to produce membrane potential (VM)-dependent inhibition and tested the prediction that such a VM-dependent inhibitor would display electrogenic binding kinetics. BTEA competitively inhibited K+ activation of Na,K-ATPase activity and steady-state 86Rb+ occlusion. The initial rate of 86Rb+ occlusion was decreased by BTEA to a similar degree whether it was added to the enzyme prior to or simultaneously with Rb+, a demonstration that BTEA inhibits the Na,K-ATPase without being occluded. Several BTEA structural analogues reversibly inhibited Na,K-pump current, but none blocked current in a VM-dependent manner except BTEA and its para-nitro derivative, pNBTEA. Under conditions that promoted electroneutral K+-K+ exchange by the Na,K-ATPase, step changes in VM elicited pNBTEA-activated ouabain-sensitive transient currents that had similarities to those produced with the K+ congener, Tl+. pNBTEA- and Tl+-dependent transient currents both displayed saturation of charge moved at extreme negative and positive VM, equivalence of charge moved during and after step changes in VM, and similar apparent valence. The rate constant (ktot) for Tl+-dependent transient current asymptotically approached a minimum value at positive VM. In contrast, k tot for pNBTEA-dependent transient current was a "U"-shaped function of VM with a minimum value near 0 mV. Homology models of the Na,K-ATPase alpha subunit suggested that quaternary amines can bind to two extracellularly accessible sites, one of them located at K+ binding sites positioned between transmembrane helices 4, 5, and 6. Altogether, these data revealed important information about electrogenic ion binding reactions of the Na,K-ATPase that are not directly measurable during ion transport by this enzyme. © 2009 American Chemical Society.
title	Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions
title_short	Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions
title_full	Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions
title_fullStr	Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions
title_full_unstemmed	Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions
title_sort	quaternary benzyltriethylammonium ion binding to the na,k-atpase: a tool to investigate extracellular k+ binding reactions
publishDate	2009
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00062960_v48_n34_p8105_Peluffo http://hdl.handle.net/20.500.12110/paper_00062960_v48_n34_p8105_Peluffo
_version_	1768545445973327872

Quaternary benzyltriethylammonium ion binding to the Na,K-ATPase: A tool to investigate extracellular K+ binding reactions

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