A study of mitochondrial membranes in relation to elementary particles (original) (raw)
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Studies on the nucleotide specificity of mitochondrial inner membrane particles
Archives of Biochemistry and Biophysics, 1969
Submitochondrial particles obtained by treatment with digitonin and by sonication were compared in order to examine the specificity of the phosphate acceptor in oxidative phosphorylation. The digitonin particles behave like intact mitochondria. They have an absolute specificity for ADP in oxidative phosphorylation and for ATP in the Pi-ATP exchange reaction. These reactions, and the 2,4-dinitrophenol-stimulated ATPase, are sensitive to atractyloside. The inhibition of oxidative phosphorylation by atractyloside is competitively reversed by ADP. The finding of Low, Vallin, and Alm that sonic particles are not absolutely specific for ADP as phosphate acceptor and are insensitive to atractyloside has been confirmed. The atractyloside sensitivity and nucleotide specificity of digitonin particles is not altered by sonication and the properties of sonic particles are not affected by treatment with digitonin. The broad phosphate acceptor specificity of sonic particles is markedly altered by the concentration of divalent cation present in the assay medium. It is concluded that it is unnecessary to invoke the existence of a nucleotide translocase enzyme to account for the differences in phosphate acceptor specificity between the two preparations. The reasons for this conclusion are discussed.
The Journal of Cell Biology, 1982
Light-membrane fractions obtained by hypoosmotic lysis of neurospora crassa mitochondria exhibit buoyant densities and marker-enzyme activities characteristic of outer mitochondrial membranes. SDS PAGE of these membrane fractions indicates that a polypeptide of M(r) 31,000 is the main protein component. Under negative-stain electron microscope examination many of the membranes in these fractions appear as large (0.5-1- mum diameter), collapsed vesicles. The surfaces of flattened, open (i.e., ripped) vesicles often exhibit extended two-dimensional arrays of subunits are arranged into hexagons within each parallelogram unit cell, 12.6x11.1 nm (lattice angle = 109 degrees).
The Journal of Cell Biology
The buoyant densities of the nuclear and mitochondrial DNA from the thoracic muscles of Sch~stocerca gregarm ,,-ere found to be 1 702 and 1.689 g/cm s, respectively, corresponding to guanine plus cytosine (G + C) content of 42.2 and 30% A prehminary treatment of the mitochondrial pellet with DNase (25°C, 20 min) is necessary to eliminate the contaminating nuclear DNA. The mitochondrml DNA renatures readily after heat denaturation and incubation at 65°C. The DNA released from the mltochondrial pellet by osmotic shock consists of circular open and closed molecules with a contour length around 5/~ The instability of insect mitochondrla in in vitro preparations is discussed.
Respiratory Properties of Mitochondria Isolated from Conidia of Neurospora crassa
Microbiology, 1981
Mitochondria from conidia of Neurospora crassa were isolated and purified by a simple and rapid technique. Electron micrographic analysis and isopycnic centrifugation on a sucrose density gradient revealed a heterogeneous pbpulation. Succinate, citrate, 2-oxoglutarate, NADH and ascorbate + tetramethyl-pphenylenediamine (TMPD) were oxidized by the mitochondria. Oxygen consumption was totally inhibited by antimycin A or cyanide. The electron transport chain was coupled to sites 1 and 2 of phosphorylation. Oligomycin, atractyloside and 2,4-dinitrophenol prevented energy coupling. I N T R O D U C T I O N Respiratory properties of mitochondria isolated from mycelia at different growth stages of Neurospora crassa wild type are now well characterized (
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1990
Rat liver mitochondria were isolated by a combination of differential and Percoll gradient centrifugation, resulting in a highly pure and intact preparation, as assessed by marker enzyme analysis, latency of cytochrome-c oxidase, respiratory control index and electron microscopy. Two different methods were compared for the separation of inner and outer membranes. In the swell-shrink-sonicate procedure glycerol was included resulting in the isolation of one outer membrane and two inner membrane fractions of high purity. Using digitonin a highly selective and gradual solubilization of the outer membrane could be accomplished. Analysis of the phospholipid composition of the intact mitochondria and all subfractions showed that the inner membrane was virtually devoid of phosphatidylinositoi and -serine, while the outer membrane contained 23% of the total mitochondriai cardiolipin, which did not originate from inner membrane contamination and therefore is a true component of the outer membrane.