Dependence of mitochondrial coenzyme A uptake on the membrane electrical gradient

Journal Article · Sun Nov 05 04:00:00 EST 1989 · Journal of Biological Chemistry; (USA)

OSTI ID:5132384

Tahiliani, A G ^[1]

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1. Weis Center for Research, Danville, PA (USA)

Coenzyme A (CoA) transport was studied in isolated rat heart mitochondria. Uptake of CoA was assayed by determining (3H)CoA associated with mitochondria under various conditions. Various oxidizable substrates including alpha-ketoglutarate, succinate, or malate stimulated CoA uptake. The membrane proton (delta pH) and electrical (delta psi) gradients, which dissipated with time in the absence of substrate, were maintained at their initial levels throughout the incubation in the presence of substrate. Addition of phosphate caused a concentration-dependent decrease of both delta pH and CoA uptake. Nigericin also dissipated the proton gradient and prevented CoA uptake. Valinomycin also prevented CoA uptake into mitochondria. Although the proton gradient was unaffected, the electrical gradient was completely abolished in the presence of valinomycin. Addition of 5 mM phosphate 10 min after the start of incubation prevented further uptake of CoA into mitochondria. A rapid dissipation of the proton gradient upon addition of phosphate was observed. Addition of nigericin or valinomycin 10 min after the start of incubation also resulted in no further uptake of CoA into with mitochondria; valinomycin caused an apparent efflux of CoA from mitochondria. Uptake was found to be sensitive to external pH displaying a pH optimum at pHext 8.0. Although nigericin significantly inhibited CoA uptake over the pHext range of 6.75-8, maximal transport was observed around pHext 8.0-8.25. Valinomycin, on the other hand, abolished transport over the entire pH range. The results suggest that mitochondrial CoA transport is determined by the membrane electrical gradient. The apparent dependence of CoA uptake on an intact membrane pH gradient is probably the result of modulation of CoA transport by matrix pH.

• OSTI ID: 5132384
• Journal Information: Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 264:31; ISSN JBCHA; ISSN 0021-9258
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
BARYONS
BODY
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CELL MEMBRANES
COENZYMES
DRUGS
ELECTROPHYSIOLOGY
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HEART
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
MAMMALS
MEMBRANE TRANSPORT
MEMBRANES
MITOCHONDRIA
NUCLEONS
ORGANOIDS
ORGANS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHYSIOLOGY
PROTONS
RATS
RODENTS
SUBSTRATES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VALINOMYCIN
VERTEBRATES