Energetic aspects of the mitochondrial biogenesis (original) (raw)
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Journal of Bioenergetics and Biomembranes, 1980
The oxidation of cytochrome b561 by ATP was measured in submitochondrial particles inhibited by antimycin. The redox potential of the bulk (M phase) was controlled by the ratio of fumarate:succinate, and the oxidation of cytochrome b was calculated and expressed as a change in redox potential (Eh) measured in millivolts. The oxidation of cytochrome b561 is an energy-driven reaction affected only by the A~b component of the proton motive force. The oxidation (measured in millivolts) is a function of the phosphate potential, reaching a maximal value of 40 mV at AG~xp <-12 kca!/mole. The maximal measured value of ATP-dependent A~b was 100 inV. Thus only a fraction of the membrane potential effects the redox state of cytochrome bs6 ~. In contrast to the ATP-induced oxidation of cytochrome b56~, cytochrome b566 is in redox equilibrium with fumarate succinate either in the presence or in the absence of ATP. The selective oxidation of b56a is explained within the term of the Q cycle as a reflection of A~b on the electron electrochemical potential. The positive electric potential of the C phase causes cytochrome b566 to act as oxidant with respect to cytochrome b56~. In the presence of antimycin cytochrome b56~ cannot equilibrate with the quinone and undergo.es oxidation, while cytochrome b566 reequilibrates with the quinone and thus regains redox equilibrium with the fumarate succinate redox buffer.
MGG Molecular & General Genetics, 1975
Yeast cells grown anaerobically have been shown to vary in their ultrastructure and absorption spectrum depending upon the composition of the growth medium. The changes observed in the anaerobically grown cells are governed by the availability of unsaturated fatty acids and ergosterol and a catabolite or glucose repression. All the cells contain nuclear and plasma membranes, but the extent of the occurrence of vacuolar and mitochondrial membranes varies greatly with the growth conditions. Cells grown anaerobically on the least nutritive medium, composed of 0.5% Difco yeast extract-5 % glucose-inorganic salts (YE-G), appear to contain little vacuolar membrane and no clearly recognizable mitochondrial profiles. Cells grown anaerobically on the YE-G medium supplemented with Tween 80 and ergosterol contain clearly recognizable vacuolar membrane and some mitochondrial profiles, albeit rather poorly defined. Cells grown on YE-G medium supplemented only with Tween 80 are characterized by the presence of large amounts of cytoplasmic membrane in addition to vacuolar membrane and perhaps some primitive mitochondrial profiles. When galactose replaces glucose as the major carbon source in the medium, the mitochondrial profiles within the cytoplasm become more clearly recognizable and their number increases. In aerobically grown cells, the catabolite repression also operates to reduce the total number of mitochondrial profiles. The possibility is discussed that cells grown anaerobically on the YE-G medium may not contain mitochondrial membrane and, therefore, that such cells, on aeration, form mitochondrial membrane from nonmitochondrial sources. A wide variety of absorption compounds is observed in anaerobically grown cells which do not correspond to any of the classical aerobic yeast cytochromes. The number and relative proportions of these anaerobic compounds depend upon the composition of the growth medium, the most complex spectrum being found in cells grown in the absence of lipid supplements.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1969
i. Pretreatment of sub-mitochondrial particles with cholate results in a change in the curve describing inhibition by antimycin of the succinate-cytochrome c reductase from sigmoidal towards linear. This effect of cholate is reversed by partial removal of the cholate by dialysis, either in the absence or presence of antimycin. 2. Treatment with cholate has the same action on the sigmoidal effect curve of antimycin on the reducibility of cytochrome b. This is also reversed by dialysis. 3. The effect of antimycin on the displacement to the red of the a-band of ferrocytochrome b, measured in the presence of succinate, NADH or reduced ubiquinone Q-2, is also described by a sigmoidal curve that is changed to a linear one by addition of cholate. 4. Linear displacement curves are obtained with menaquinol or Na2S20 4. 5. It is proposed that antimycin is an allosteric inhibitor of the respiratory chain. This allosteric effect should be distinguished from the effect of antimycin on the "conformation stability" of Complex III.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1970
I. The oligomycin-sensitive Mg~+-dependent ATPase activity of mitochondria isolated from wild-type yeastSaccharomyces cerevisiae was only slightly inhibited by atractyloside at concentrations which entirely prevented oxidative phosphorylation. This indicated that most of the ATPase in these mitochondrial preparations was located outside the atractyloside-sensitive barrier and did not participate in the energy-transfer process. 2. ATPase activity of mitochondria isolated from nuclear gene mutants deficient in a single cytochrome, a, b, or c, respectively, was strongly inhibited by oligomycin. The mitochondria from these mutants, like those from the wild-type strain, were able to incorporate amino acids into protein. 3. Mitochondrial ATpase activity of single nuclear gene mutants deficient in both cytochromes a and b was only slightly inhibited by oligomycin. These mitochondria were incapable of incorporating amino acids into protein. The mitochondria from these nuclear mutants thus resembled mitochondria of cytoplasmic respirationdeficient mutants. 4. The results suggest that mitochondrial cytochromes may be coded by nuclear genes and that product(S) of mitochondrial protein synthesis may be required for integrating the cytochromes a and b and the components of the oligomycin-sensitive ATPase complex into the mitochondrial membranes.
Dynamic Control on the Rate of the Reduction of the b Type Cytochromes in Submitochondrial Particles
European Journal of Biochemistry, 1975
In the presence of antimycin and KCN the reduction of cytochrome b in phosphorylating submitochondrial particles followed a biphasic first-order kinetics. The transition from the first, rapid phase to the second, slow phase occurred while the reduction of cytochromes c + c1 and a through or around the antimycin block was still linear with time. Thus, the phase transition was due to a fall-off in the rate of cytochrome b reduction.
Evidence of Antimycin-Insensitive Respiration in a Commercial Brewing Yeast
Journal of the Institute of Brewing, 1999
Tlte presence of antimycin-insensitive respiration in an industrial brewing yeast strain (Saccharomyces cerevisiae AJL 2036) was confirmed by studying the effects of antimycin A (inhibits electron transfer from cyt b to ct) on brewing yeast performance in the presence and absence of oxygen. The inhibitor sodium azide was also used to assess whether blocking electron transfer further downstream of the antimycin-effective site eliminated the enhanced fermentation parameters observed in the presence of antimycin A. Oligomycin, an inhibitor of the mitrochondrial membrane ATPase, was also used to determine the importance of intramitochondrial ATP synthesis on the observed effects. Fermentations were monitored for overall performance and beer quality indicators. Tlte measured parameters showed no changes due to oligomycin addition indicating that the major source of energy in the cells was cytoplasmically-generated via glycolysis. Results from the fermentations in the presence of antimycin A confirmed the existence of an alternative respiratory pathway, the stimulation of which resulted in improved fermentative performance. It is postulated that antimycin A enhanced the fermentation rate by increasing the amount of yeast growth. This caused a direct pull on yeast metabolism including fermentative activity. The mechanism was postulated to involve an increased supply of critical growth intermediates in the presence of antimycin A rather than an increased intramitochondrial energy supply per se.