valinomycin and 1-10-phenanthroline

We report studies of the import into mitochondria of MTF1, a nucleus-encoded factor that markedly stimulates the specific transcription of mitochondrial DNA. Unlike most of the mitochondrial precursor proteins studied so far, import of MTF1 does not appear to require a receptor on the outer membrane, membrane potential across the inner membrane, or ATP hydrolysis. Its import is not affected by low temperature. It lacks a cleavable presequence but translocates across the inner membrane through its amino terminus; its sorting is independent of hsp60. Our results indicate an unusual and distinct import pathway for MTF1 into the yeast mitochondria.

Topics: Biological Transport; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Cell Nucleus; Digitonin; Edetic Acid; Endopeptidase K; Fungal Proteins; Intracellular Membranes; Membrane Potentials; Mitochondria; Mitochondrial Proteins; Phenanthrolines; Protein Precursors; Recombinant Fusion Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Serine Endopeptidases; Temperature; Transcription Factors; Trypsin; Valinomycin

Effects of the S-S cross-linking reagent, Cu2+-o-phenanthroline (CuP), on salt conductances of gastric vesicle membranes in which the (H+ + K+)-ATPase is present were studied. CuP caused a dose-dependent increase in the KCl conductance of the vesicle membrane. The increase of the KCl conductance caused by 10 microM CuP was completely prevented by 0.3 mM ATP or 0.3 mM adenyl 5'-yl imidodiphosphate and partially prevented by ADP. The NaCl conductance was also increased by the CuP reaction. However, CuP has no effect on the K2SO4 conductance. Pretreatments of vesicles with 0.1 mM 4-acetoamide-4'-isothiocyanostilbene-2,2'-disulfonate, an anion channel inhibitor, completely blocked the effect of CuP. Thus, these effects of CuP are ascribable to the increase in the anion conductance of the vesicle membrane produced by S-S cross-linking. Furthermore, tyrosine-tyrosine cross-linking with tetranitromethane also increases the anion conductance. Probable roles of the opening of the closed anion channel of the ATPase were discussed in regard to the acid secretory mechanism of gastric mucosa.

Topics: Adenosine Triphosphatases; Animals; Disulfides; Gastric Mucosa; H(+)-K(+)-Exchanging ATPase; Kinetics; Phenanthrolines; Potassium Chloride; Swine; Tetranitromethane; Valinomycin

1. When cytochrome c2 is available for oxidation by the photosynthetic reaction centre, the decay of the carotenoid absorption band shift generated by a short flash excitation of Rhodopseudomonas capsulata chromatophores is very slow (half-time approximately 10 s). Otherwise the decay is fast (half-time approximately 1 s in the absence and 0.05 s in the presence of 1,10-ortho-phenanthroline) and coincides with the photosynthetic back reaction. 2. In each of these situations the carotenoid shift decay, but not electron transport, may be accelerated by ioniophores. The ionophore concentration dependence suggests that in each case the carotenoid response is due to a delocalised membrane potential which may be dissipated either by the electronic back reaction or by electrophoretic ion flux. 3. At high redox potentials, where cytochrome c2 is unavailable for photooxidation, electron transport is believed to proceed only across part of the membrane dielectric. Under such conditions it is shown that the driving force for carbonyl cyanide trifluoromethoxyphenyl hydrazone-mediated H+ efflux is nevertheless decreased by valinomycin/K+; demonstrating that the [BChl]2 leads to Q electron transfer generates a delocalised membrane potential.

Topics: Bacterial Chromatophores; Bacteriochlorophylls; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; Carotenoids; Electron Transport; Membrane Potentials; Oxidation-Reduction; Phenanthrolines; Photosynthesis; Rhodopseudomonas; Spectrophotometry; Valinomycin