A vacuolar-type proton pump in a vesicle fraction enriched with potassium transporting plasma membranes from tobacco hornworm midgut

Journal Article · Wed Jul 05 00:00:00 EDT 1989 · J. Biol. Chem.; (United States)

OSTI ID:5696240

Wieczorek, H; Weerth, S; Schindlbeck, M; Klein, U

Mg-ATP dependent electrogenic proton transport, monitored with fluorescent acridine orange, 9-aminoacridine, and oxonol V, was investigated in a fraction enriched with potassium transporting goblet cell apical membranes of Manduca sexta larval midgut. Proton transport and the ATPase activity from the goblet cell apical membrane exhibited similar substrate specificity and inhibitor sensitivity. ATP and GTP were far better substrates than UTP, CTP, ADP, and AMP. Azide and vanadate did not inhibit proton transport, whereas 100 microM N,N'-dicyclohexylcarbodiimide and 30 microM N-ethylmaleimide were inhibitors. The pH gradient generated by ATP and limiting its hydrolysis was 2-3 pH units. Unlike the ATPase activity, proton transport was not stimulated by KCl. In the presence of 20 mM KCl, a proton gradient could not be developed or was dissipated. Monovalent cations counteracted the proton gradient in an order of efficacy like that for stimulation of the membrane-bound ATPase activity: K+ = Rb+ much greater than Li+ greater than Na+ greater than choline (chloride salts). Like proton transport, the generation of an ATP dependent and azide- and vanadate-insensitive membrane potential (vesicle interior positive) was prevented largely by 100 microM N,N'-dicyclohexylcarbodiimide and 30 microM N-ethylmaleimide. Unlike proton transport, the membrane potential was not affected by 20 mM KCl. In the presence of 150 mM choline chloride, the generation of a membrane potential was suppressed, whereas the pH gradient increased 40%, indicating an anion conductance in the vesicle membrane. Altogether, the results led to the following new hypothesis of electrogenic potassium transport in the lepidopteran midgut. A vacuolar-type electrogenic ATPase pumps protons across the apical membrane of the goblet cell, thus energizing electroneutral proton/potassium antiport. The result is a net active and electrogenic potassium flux.

• Research Organization: Univ. of Munich (Germany, F.R.)
• OSTI ID: 5696240
• Journal Information: J. Biol. Chem.; (United States), Vol. 264:19
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ATP-ASE
ENZYME ACTIVITY
IMIDES
BIOLOGICAL EFFECTS
POTASSIUM
MEMBRANE TRANSPORT
VANADIUM
ATP
CATIONS
CELL MEMBRANES
DYES
LARVAE
LITHIUM
MOTHS
NUCLEOTIDES
PROTONS
RUBIDIUM
ACID ANHYDRASES
ALKALI METALS
ANIMALS
ARTHROPODS
BARYONS
CELL CONSTITUENTS
CHARGED PARTICLES
ELEMENTARY PARTICLES
ELEMENTS
ENZYMES
FERMIONS
HADRONS
HYDROLASES
INSECTS
INVERTEBRATES
IONS
LEPIDOPTERA
MEMBRANES
METALS
NUCLEONS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHOHYDROLASES
TRANSITION ELEMENTS
560300* - Chemicals Metabolism & Toxicology