Electrophysiological Evidence for an Electrogenic Proton Pump and the Proton Symport of Glucose in the Marine FungusDendryphiella salina

1990 ◽  
Vol 41 (4) ◽  
pp. 449-456 ◽  
Author(s):  
J. M. DAVIES ◽  
C. BROWNLEE ◽  
D. H. JENNINGS
Keyword(s):  
Proton Pump ◽  
Electrophysiological Evidence ◽  
Proton Symport ◽  
Electrogenic Proton Pump

scholarly journals Golgi membranes contain an electrogenic H+ pump in parallel to a chloride conductance.

1983 ◽  
Vol 97 (4) ◽  
pp. 1303-1308 ◽  
Author(s):  
J Glickman ◽  
K Croen ◽  
S Kelly ◽  
Q Al-Awqati
Keyword(s):  
Membrane Potential ◽  
Proton Pump ◽  
Gradient Centrifugation ◽  
Chloride Conductance ◽  
F1 Atpase ◽  
Chloride Uptake ◽  
Golgi Vesicles ◽  
Galactosyl Transferase ◽  
Golgi Membranes ◽  
Electrogenic Proton Pump

Rat liver Golgi vesicles were isolated by differential and density gradient centrifugation. A fraction enriched in galactosyl transferase and depleted in plasma membrane, mitochondrial, endoplasmic reticulum, and lysosomal markers was found to contain an ATP-dependent H+ pump. This proton pump was not inhibited by oligomycin but was sensitive to N-ethyl maleimide, which distinguishes it from the F0-F1 ATPase of mitochondria. GTP did not induce transport, unlike the lysosomal H+ pump. The pump was not dependent on the presence of potassium nor was it inhibited by vanadate, two of the characteristics of the gastric H+ ATPase. Addition of ATP generated a membrane potential that drove chloride uptake into the vesicles, suggesting that Golgi membranes contain a chloride conductance in parallel to an electrogenic proton pump. These results demonstrate that Golgi vesicles can form a pH difference and a membrane potential through the action of an electrogenic proton translocating ATPase.

scholarly journals The insect V-ATPase, a plasma membrane proton pump energizing secondary active transport: molecular analysis of electrogenic potassium transport in the tobacco hornworm midgut.

1992 ◽  
Vol 172 (1) ◽  
pp. 335-343 ◽  
Author(s):  
H Wieczorek
Keyword(s):  
Plasma Membrane ◽  
Proton Pump ◽  
Cdna Probe ◽  
Motive Force ◽  
Solute Fluxes ◽  
K Secretion ◽  
Electrogenic Proton Pump ◽  
Apical Membranes ◽  
High Degree ◽  
Plasma Membrane Proton Pump

Goblet cell apical membranes in the larval midgut of Manduca sexta are the site of active and electrogenic K+ secretion. They possess a vacuolar-type ATPase which, in its immunopurified form, consists of at least nine polypeptides. cDNAs for the A and B subunits screened by monoclonal antibodies to the A subunit of the Manduca V-ATPase or by hybridisation with a cDNA probe for a plant V-ATPase B subunit have been cloned and sequenced. There is a high degree of identity to the sequences of the respective subunits of other V-ATPases. The M. sexta plasma membrane V-ATPase is an electrogenic proton pump which energizes, by the electrical component of the proton-motive force, electrogenic K+/nH+ antiport, resulting in net electrogenic K+ secretion. Since the midgut lacks a Na+/K(+)-ATPase, all solute fluxes in this epithelium seem to be energized by the V-ATPase. Thus, the midgut provides an alternative to the classical concept of animal plasma membrane energization by the Na(+)-motive force generated by the Na+/K(+)-ATPase.

Evidence for the Presence of an Electrogenic Proton Pump on the Trout Gill Epithelium

1991 ◽  
Vol 161 (1) ◽  
pp. 119-134 ◽  
Author(s):  
HONG LIN ◽  
DAVID RANDALL
Keyword(s):  
Proton Pump ◽  
Water Proton ◽  
Gill Epithelium ◽  
Blood Ph ◽  
Water Ph ◽  
Electrogenic Proton Pump ◽  
Proton Excretion ◽  
Transport Inhibitors ◽  
Trout Gill ◽  
Transfer Mechanisms

Ion transport inhibitors, amiloride, SITS, vanadate and acetazolamide, wereadded to the water to determine the effect of ion transfer mechanisms on the acidification of water passing over the gills. In neutral water, proton excretion causes a marked reduction in gill water pH. If water pH is 2.5 units lower than blood pH, however, then this proton excretion is inhibited and all water pH changes can be accounted for by CO2 hydration and ammonia protonation. Proton excretion across the gills is insensitive to 0.1mmoll−1 amiloride and SITS but sensitive to vanadate, acetazolamide and water pH; thus, we conclude that proton excretion is mediated by an active proton pump on the apical membrane of the gill epithelium similar to that reported for the frog skin. Higher concentrations of amiloride (0.5 and 1mmoll−1) reduced both ammonia and acid excretion, presumably because of inhibition of Na+/K+-ATPase on the basolateral border ofthe gill epithelium.

scholarly journals A potassium-proton symport in Neurospora crassa.

1986 ◽  
Vol 87 (5) ◽  
pp. 649-674 ◽  
Author(s):  
A Rodriguez-Navarro ◽  
M R Blatt ◽  
C L Slayman
Keyword(s):  
Neurospora Crassa ◽  
Proton Pump ◽  
Higher Plants ◽  
Free Calcium ◽  
Primary Proton ◽  
Uptake System ◽  
Charge Balance ◽  
Proton Symport ◽  
Electrophysiological Measurements ◽  
Spherical Cells

Combined ion flux and electrophysiological measurements have been used to characterized active transport of potassium by cells of Neurospora crassa that have been moderately starved of K+ and then maintained in the presence of millimolar free calcium ions. These conditions elicit a high-affinity (K1/2 = 1-10 microM) potassium uptake system that is strongly depolarizing. Current-voltage measurements have demonstrated a K+-associated inward current exceeding (at saturation) half the total current normally driven outward through the plasma membrane proton pump. Potassium activity ratios and fluxes have been compared quantitatively with electrophysiological parameters, by using small (approximately 15 micron diam) spherical cells of Neurospora grown in ethylene glycol. All data are consistent with a transport mechanism that carries K ions inward by cotransport with H ions, which move down the electrochemical gradient created by the primary proton pump. The stoichiometry of entry is 1 K ion with 1 H ion; overall charge balance is maintained by pumped extrusion of two protons, to yield a net flux stoichiometry of 1 K+ exchanging for 1 H+. The mechanism is competent to sustain the largest stable K+ gradients that have been measured in Neurospora, with no direct contribution from phosphate hydrolysis or redox processes. Such a potassium-proton symport mechanism could account for many observations reported on K+ movement in other fungi, in algae, and in higher plants.

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