Publications (7)14.26 Total impact
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Article: Lipid-protein interactions in the outer membranes of yeast and rat liver mitochondria.
Archives of Biochemistry and Biophysics 10/1976; 176(1):1-11. · 2.93 Impact Factor -
Article: The biogenesis of mitochondrial membranes in the yeast Saccharomyces cerevisiae.
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ABSTRACT: Membrane lipids of yeast mitochondria have been enriched by growing yeast cells in minimal medium supplemented with specific unsaturated fatty acids as the sole lipid supplement. Using the activity of marker enzymes for the outer (kynurenine hydroxylase) and inner (cytochrome c oxidase and oligomycin-sensitive ATPase) mitochondrial membranes, Arrhenius plots have been constructed using both promitochondria and mitochondria obtained from O2-adapting cells in the presence of a second unsaturated fatty acid (i.e. linoleate (N2) to elaidic (O2)). Transition temperatures which reflect the unsaturated fatty acid enrichment of the new membranes reveal interesting features involved in the mechanism of the assembly of these two mitochondrial membranes. This approach was further enforced with both lipid depletion and mitochondrial protein inhibition studies. Kynurenine hydroxylase which does not require fatty acid for its continued synthesis during aerobiosis seems to be incorporated into the preformed linoleate-anaerobic outer membrane. The newly synthesized activities of inner mitochondrial membrane enzymes on the other hand, appear to integrate their activity into newly formed aerobic-elaidic-rich inner membrane. These latter enzymes show a distinct dependence on fatty acid supplement for their continued synthesis during their aerobic phase. This suggests that O2-dependent proteo-lipid precursors are formed before these enzymes are integrated into their membrane mosaic. Two separate models are proposed to explain these results, one for the lipid-rich outer mitochondrial membrane and another for the protein-rich inner mitochondrial membrane.Biochimica et Biophysica Acta 03/1975; 375(3):446-61. · 4.66 Impact Factor -
Article: The incorporation of cytochrome oxidase into newly-forming yeast mitochondrial membranes
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ABSTRACT: Cytochrome c oxidase extracted from a yeast auxotroph grown on different fatty acid supplements, and assayed at various temperatures (037), gives transition points (Tt) when the data are expressed in an Arrhenius plot: Tt for linoleic, oleic and elaidic acids were 7.7, 10.2 and 21.8 respectively. Lipid anlaysis of isolated mitochondria established that there is a change in lipid profile when yeast is first grown aerobically on linoleic acid and then transferred to elaidic acid under anaerobic consitions. These two observations bave been used as a basis for the investigation of the assembly of cytochrome c oxidase when cells are oxygen induced for mitochondriogenesisvia a linoleic, N2 elaidic, O2 transfer experiment. A three-stage assembly process is proposed consisting of (i) 0.00.25 h, auto-assembly of oxidase from preformed, chloramphenicol-sensitive precursors and newly synthesized cycloheximide-sensitive precursors, (ii) 0.25 h0.5h, a continuation of (i) plusde novo synthesis of new precursors of both kinds and (iii) 0.5 h onwards; normal, synchronisedde novo synthesis. This model predicts one population of oxidase molecules at 0.0 h (linoleic Tt) and two populations of oxidase at 0.5 h (end of stage (ii)); one from the anaerobic precursors (linoleic Tt) and one for thede nove, aerobic oxidase (elaidic Tt): these predictions are confirmed by Arrhenius profiles constructed from samples taken at 0.0, 0.5, 1.0 and 3.0 h after oxygen challenge.Journal of Bioenergetics 06/1974; 6(4):135-150. · 2.81 Impact Factor -
Article: The effect of altered membrane-lipid composition on enzyme activities of outer and inner mitochondrial membranes of Saccharomyces cerevisiae.
Biochemical and Biophysical Research Communications 03/1974; 56(4):1078-85. · 2.48 Impact Factor -
Article: Mitochondriogenesis: a comparative study of some commonly used strains of Saccharomyces cerevisiae.
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ABSTRACT: In view of the numerous different yeast strains which are used in studies of mitochondriogenesis, we considered that a comparative study of some of these strains would provide useful information for workers in this field. To this end, we have compared the growth characteristics of several widely used strains and of some randomly selected strains from our culture collection. The yeast were grown on glucose, both aerobically and anaerobically; parameters studied included ethanol metabolism, respiratory quotients, growth rates, and carbon source utilization.The nine strains can be divided into three classes : class 1, Brewers yeast showing very fast fermentation and high ethanol yields together with a pronounced diauxic, aerobic growth curve; class 2, wine yeasts with a slower fermentation rate, lower ethanol yields, and poorer growth under anaerobic conditions; class 3, a miscellaneous collection including auxotrophs, petites, and an obligate aerobic yeast.It is concluded that a large proportion of the work done on mitochondriogenesis has been performed on similar yeast strains but that some caution must be exercised when comparing yeasts from different classes.Canadian Journal of Microbiology 09/1971; 17(8):1125-31. · 1.36 Impact Factor -
Article: The effect of altered membrane-lipid composition on enzyme activities of outer and inner mitochondrial membranes of Saccharomyces cerevisiae
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ABSTRACT: Enrichment of yeast mitochondrial membranes with specific unsaturated fatty acids was achieved by growing this organism in minimal medium supplemented with the desired unsaturated fatty acid. The alteration in the membrane lipid milieu resulted in changes in both catalytic and Arrhenius kineties of enzymes characteristic of the outer and inner mitochondrial membranes. The implication that lipids are involved in the expression of the activity of kyneurine hydroxylase, a marker enzyme of the outer mitochondrial membrane, is presented.Biochemical and Biophysical Research Communications. -
Article: The biogenesis of mitochondrial membranes in the yeast Saccharomyces cerevisiae
[show abstract] [hide abstract]
ABSTRACT: Membrane lipids of yeast mitochondria have been enriched by growing yeast cells in minimal medium supplemented with specific unsaturated fatty acids as the sole lipid supplement. Using the activity of marker enzymes for the outer (kynurenine hydroxylase) and inner (cytochrome c oxidase and oligomycin-sensitive ATPase) mitochondrial membranes, Arrhenius plots have been constructed using both pro-mitochondria and mitochondria obtained from O2-adapting cells in the presence of a second unsaturated fatty acid (i.e. linoleate (N2) to elaidic (O2)). Transition temperatures which reflect the unsaturated fatty acid enrichment of the new membranes reveal interesting features involved in the mechanism of the assembly of these two mitochondrial membranes. This approach was further enforced with both lipid depletion and mitochondrial protein inhibition studies. Kynurenine hydroxylase which does not require fatty acid for its continued synthesis during aerobiosis seems to be incorporated into the preformed linoleate-anaerobic outer membrane. The newly synthesized activities of inner mitochondrial membrane enzymes on the other hand, appear to integrate their activity into newly formed aerobic-elaidic-rich inner membrane. These latter enzymes show a distinct dependence on fatty acid supplement for their continued synthesis during their aerobic phase. This suggests that O2-dependent proteo-lipid precursors are formed before these enzymes are integrated into their membrane mosaic. Two separate models are proposed to explain these results, one for the lipid-rich outer mitochondrial membrane and another for the protein-rich inner mitochondrial membrane.Biochimica et Biophysica Acta (BBA) - Biomembranes.
