Increase of local hydrogen ion gradient near bilayer lipid membrane under the conditions of catalysis of proton transfer across the interface

Abstract

The measurements of pH profiles in the unstirred layers (USLs) near planar bilayer lipid membranes (BLM) were applied for the evaluation of the hydrogen ion fluxes which were induced by nigericin in the presence of potassium ion gradients. It was shown that at high concentrations of KCl the increase in the concentration of citrate buffer caused an anomalous effect, namely, an increase in the local pH shifts in the USLs. The hydrogen ion flux rose 50 times upon the increase in the citrate concentration from 1 mM to 20 mM. Phosphate stimulated the flux 7 times under these conditions. In agreement with our previous results, at low KCl concentrations, when the process is limited by the K + -nigericin interaction, an increase in the buffer concentration led to a reduction of the local pH shifts, under these conditions the usual concentration dependence was observed. The data obtained favor the model implying the existence of the kinetic barrier for proton transfer at the membrane-water interface.z 1998 Federation of European Biochemical Societies.

Cardiolipin, Non-Bilayer Structures and Mitochondrial Bioenergetics: Relevance to Cardiovascular Disease

“…The excess of protons on the interface driving ATP synthesis was shown for the first time in the octane-water model [ 123 ]. A kinetic barrier on membrane surface does not allow H + ions to detach immediately into the solution [ 124 , 125 ], which results in short-distance lateral transfer of H + ions from proton pumps to ATP synthases within a tightly clustered OXPHOS system [ 126 ]. Indeed, lateral movement of protons on membrane surface that drives ATP synthesis has been observed in mitochondria and mitoplasts [ 127 , 128 ].…”

Non-bilayer Lipid Phases Modulate the Structure and Functions of Mitochondrial Membranes: Pharmacological Relevance

“…The idea of protons diffusing between the ETC proteins along the inner crista membrane surface was first suggested in 1961 [118] and it was convincingly corroborated one and a half decades later in the octane-water interface system [119]. About two decades later, the existence of a kinetic barrier for proton transfer from a membrane surface to bulk water was reported [120] and a few more years later a proton transfer across the interface under conditions of catalysis and driven by proton gradient on the membrane surface was demonstrated [121]. Four more years later, a metastable bond between protons and mitoplast surface [122] and protons from Brønsted acid bounded to the mitochondrial surface and serving as a substrate for ATP synthase was reported [123].…”

Oligomeric hypercomplex of the complete oxidative phosphorylation system in heart mitochondria

“…The situation changed when the formation of membrane-bound hydrogen ions was detected on the membrane-water interface after transmembrane proton transfer (26,27). Membrane-bound protons carry free energy excess but do not detach from the membrane due to the existence of kinetic barrier (26).…”

“…After transmembrane transfer protons do not immediately detach from the membrane [3] due to the existence of kinetic barrier [4,5], therefore OXPHOS clustering can be energetically beneficial. Protons on the membrane surface have a high lateral mobility [6–9], which enables their transfer for the short distances along the membrane without detachment into the bulk phase.…”