Ca/sup 2 +/ transport against its electrochemical gradient in cytochrome oxidase vesicles reconstituted with mitochondrial hydrophobic proteins
Control experiments verified that the energization conditions used produced appropriately oriented membrane potentials. Partially purified hydrophobic mitochondria protein complexes were found to be less effective than complex V. The reconstituted system showed cation selectivity since Ca/sup 2 +/, Mn/sup 2 +/, and Rb/sup +/ were transported, while Na/sup +/ was not. Low levels of uncoupler, which did not affect oxidation rates, were found to partially inhibit Ca/sup 2 +/ uptake regardless of the membrane potential polarity. Uncoupling levels of uncoupler markedly inhibited Ca/sup 2 +/ uptake in internally negative cytochrome oxidase vesicles; however, inhibition in internally positive cytochrome oxidase vesicles was less relative to that at lower levels of uncoupler. The uncoupling combination of nigericin, valinomycin, and K/sup +/ was inhibitory to uptake regardless of membrane potential polarity. A reconstituted system of oxidative phosphorylation, which contains a hydrophobic protein fraction, energized with cytochrome oxidase similarly accumulated Ca/sup 2 +/ despite formation of an internally positive membrane potential. The results suggest that cytochrome oxidase, when coupled to appropriate hydrophobic mitochondrial proteins, can act as an electrogenic Ca/sup 2 +/ pump deriving its energy directly from electron transport. (JMT)
- Research Organization:
- Univ. of Rochester, NY
- DOE Contract Number:
- AC02-76EV03490
- OSTI ID:
- 5212397
- Journal Information:
- Arch. Biochem. Biophys.; (United States), Journal Name: Arch. Biochem. Biophys.; (United States) Vol. 210:2; ISSN ABBIA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ALKALI METALS
ALKALINE EARTH METALS
CALCIUM
CATIONS
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
COMPLEXES
CYTOCHROME OXIDASE
ELEMENTS
ENERGY TRANSFER
ENZYMES
HAEM DEHYDROGENASES
INHIBITION
IONS
MANGANESE
MEMBRANES
METALS
MITOCHONDRIA
ORGANIC COMPOUNDS
ORGANOIDS
OXIDOREDUCTASES
PROTEINS
RUBIDIUM
SODIUM
TRANSITION ELEMENTS
UPTAKE