COUPLING OF PROTON SOURCE AND SINK VIA H-MIGRATION ALONG THE MEMBRANE-SURFACE AS REVEALED BY DOUBLE PATCH-CLAMP EXPERIMENTS()

Long-range proton transfer along the surface of black lipid bilayers w as observed between two integral membrane channels (gramicidins), one operating as a proton source, the other as a sink, by patch-clamp tech nique. In contrast, potassium ions were shown to equilibrate with the aqueous bulk phase before being consumed. Both channels opened and clo sed simultaneously only if the charge between them was carried by prot ons. In this case an anomalous high conductance between two patched me mbrane fragments was measured, each of them containing one single gram icidin channel. The coupled state disappeared when the distance betwee n these two channels was increased above the critical value, The latte r was shown to increase with the channel lifetime. Our results support the idea of the 'localized' proton coupling, in which protons that ha ve been pumped across membranes migrate along the membrane surface to reach another membrane protein that utilizes the established pH gradie nt. (C) 1998 Federation of European Biochemical Societies.