scholarly journals The vectorial orientation of human monoamine oxidase in the mitochondrial outer membrane

1979 ◽  
Vol 181 (1) ◽  
pp. 7-14 ◽  
Author(s):  
S M Russell ◽  
J Davey ◽  
R J Mayer
Keyword(s):  
Monoamine Oxidase ◽  
Outer Membrane ◽  
Outer Surface ◽  
Human Liver ◽  
Brain Cortex ◽  
Mitochondrial Outer Membrane ◽  
Inner Surface

1. The localization of monoamine oxidase in the mitochondrial outer membrane was studied in preparations of human liver mitochondrial and brain-cortex non-synaptosomal and synaptosomal mitochondria. 2. Immunochemical accessibility in iso-osmotic and hypo-osmotic mitochondrial preparations was used to localize the enzyme. 3. It was shown that the immunochemically accessible tyramine-oxidizing activity was distributed approximately equally on both surfaces of the membrane in human liver and brain-cortex non-synaptosomal mitochondria. However, the immunochemically accessible beta-phenethylamine-oxidizing activity was situated predominantly on the outer surface, and the immunochemically accessible 5-hydroxytryptamine-oxidizing activity was situated predominantly on the inner surface of the mitochondrial outer membrane in liver and brain-cortex non-synaptosomal mitochondrial preparations. 4. Considerable variation in the distribution of the enzyme in preparations of synaptosomal mitochondria was seen. 5. The simplest model consistent with our observations is that, in liver and brain-cortex non-synaptosomal mitochondria, the tyramine-oxidizing activity is distributed on both sides of the mitochondrial outer membrane, the beta-phenethylamine-oxidizing activity is located on the outer surface of the outer membrane and the 5-hydroxytryptamine-oxidizing activity is located on the inner surface of the mitochondria outer membrane

scholarly journals Immunochemical characterization of monoamine oxidase from human liver, placenta, platelets and brain cortex

1979 ◽  
Vol 181 (1) ◽  
pp. 15-20 ◽  
Author(s):  
S M Russell ◽  
J Davey ◽  
R J Mayer
Keyword(s):  
Enzyme Activity ◽  
Monoamine Oxidase ◽  
Liver Enzyme ◽  
Human Liver ◽  
Brain Cortex ◽  
Lipid Binding ◽  
Mitochondrial Preparation ◽  
Immunochemical Characterization ◽  
Immunodiffusion Analysis

1. Antiserum raised to purified human liver monoamine oxidase was used to characterize the monoamine oxidase from human liver, brain cortex, placenta and platelets. 2. Antibodies to monoamine oxidase were purified by adsorption with a mitochondrial preparation. 3. Monoamine oxidase was present in liver particle-free supernatant as measured by enzyme activity and immunodiffusion. 4. Multiple precipitin lines were obtained on immunodiffusion analysis against the purified liver enzyme. It is proposed that this is due to either aggregation or to differential lipid binding. 5. The results suggest that the functionally different enzymes found in liver, brain cortex, platelets and placenta are immunochemically related and may be identical.

scholarly journals Comparison of the degradative fate of monoamine oxidase in endogenous and transplanted mitochondrial outer membrane in rat hepatocytes. Implications for the cytomorphological basis of protein catabolism

1984 ◽  
Vol 219 (1) ◽  
pp. 61-72 ◽  
Author(s):  
P J Evans ◽  
R J Mayer
Keyword(s):  
Monoamine Oxidase ◽  
Outer Membrane ◽  
Membrane Vesicles ◽  
Fluorescein Isothiocyanate ◽  
Rat Hepatocytes ◽  
Similar Rate ◽  
Outer Membrane Vesicles ◽  
Mitochondrial Outer Membrane ◽  
Protein Catabolism

The degradative fate of monoamine oxidase in endogenous and transplanted mitochondrial outer membrane has been compared in rat hepatocyte monolayers. Monoamine oxidase was specifically irreversibly radiolabelled by the suicide inhibitor [3H]pargyline. Hepatocyte monolayers were cultured in conditions in which rates of protein catabolism like those in vivo are maintained [Evans & Mayer (1983) Biochem. J. 216, 151-161]. Incubation of hepatocyte monolayers for 17 h with [3H]pargyline specifically radiolabels mitochondrial monoamine oxidase, as shown by Percoll-gradient fractionation of broken hepatocytes. Monoamine oxidase is degraded at a similar rate to that observed in liver in vivo (t1/2 approx. 63 h). The effects of leupeptin, methylamine and colchicine on the degradation of endogenous radiolabelled enzyme has been studied over prolonged culture periods. Culture of hepatocytes for periods of up to 80 h with inhibitors was not cytotoxic, as demonstrated by measurements of several intrinsic biochemical parameters. Leupeptin, methylamine and colchicine inhibit the degradation of endogenous monoamine oxidase by 60, 38 and 18% respectively. Monoamine oxidase in mitochondrial-outer-membrane vesicles introduced into hepatocytes by poly(ethylene glycol)-mediated vesicle-cell transplantation is degraded at a similar rate (t1/2 55 h) to the endogenous mitochondrial enzyme. Whereas leupeptin inhibits the degradation of endogenous and transplanted enzyme to a similar extent, methylamine and colchicine inhibit the degradation of transplanted enzyme to a much greater extent (85 and 56% respectively). Fluorescence microscopy (with fluorescein isothiocyanate-conjugated mitochondrial outer membrane) shows that transplanted mitochondrial outer membrane undergoes internalization and translocation to a sided perinuclear site, as observed previously with whole mitochondria [Evans & Mayer (1983) Biochem. J. 216, 151-161]. The effects of the inhibitors on the distribution of transplanted membrane material in the cell and inhibition of proteolysis show the importance of cytomorphology for intracellular protein catabolism.

scholarly journals Procaspase-9 is attached to the mitochondrial outer membrane in the early stages of apoptosis

2007 ◽  
Vol 12 (4) ◽  
Author(s):  
Irina Milisav ◽  
Dušan Šuput
Keyword(s):  
Outer Membrane ◽  
Outer Surface ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Rat Hepatocytes ◽  
Mitochondrial Outer Membrane ◽  
Cell Type ◽  
Caspase 9 ◽  
Mitochondrial Protein Import ◽  
Cellular Location

AbstractProcaspase-9 is the zymogen form of one of the apoptosis initiators, caspase-9. Its cellular location may differ depending on the cell type; it is found throughout the cytosol, although some of it may be associated with the mitochondria. Procaspase-9 relocates from the cytosol to the mitochondria shortly after the triggering of apoptosis in rat hepatocytes. We investigated whether the mitochondrial protein import machineries import procaspase-9. The combined results of protein import analyses, mitochondrial fractionation and protease treatments of intact and swollen mitochondria imply that procaspase-9 attaches to the outer surface of the mitochondrial outer membrane.

scholarly journals Degradation of transplanted mitochondrial proteins by hepatocyte monolayers

1983 ◽  
Vol 216 (1) ◽  
pp. 151-161 ◽  
Author(s):  
P J Evans ◽  
R J Mayer
Keyword(s):  
Acid Phosphatase ◽  
Monoamine Oxidase ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Mitochondrial Proteins ◽  
Mitochondrial Outer Membrane ◽  
Lag Period

Reductively [3H]methylated rat mitochondria and mitochondrial-outer-membrane vesicles and mitochondrial-outer-membrane vesicles where monoamine oxidase is irreversibly labelled by [3H]pargyline have been transplanted into hepatocytes by poly(ethylene glycol)-mediated organelle or organelle-vesicle cell fusion. During subsequent culture of hepatocyte monolayers for 4-5 days, under conditions which mimic endogenous catabolic rates in vivo the transplanted organelle proteins retain their degradation characteristics observed in vivo (e.g. mitochondria: average t 1/2 72.5 h; monoamine oxidase: t1/2 55 h). In all cases protein degradation with first-order kinetics is only observed after an initial lag period (i.e. 24-30 h after fusion). Transplantation of fluorescein-conjugated organelles showed that the fluorescent material is rapidly internalized (average t1/2 1-6 h) and uniformly distributed in the cytoplasm. During a subsequent 18-24 h period (which corresponds to the lag period for intracellular destruction of transplanted mitochondrial material) the transplanted material is translocated to assume a perinuclear distribution. The destruction of transplanted mitochondrial proteins is compared with endogenous mitoribosomally synthesized proteins (average t1/2 52.5 h). Percoll fractionation of cell homogenates containing transplanted mitochondrial outer membranes where the enzyme monoamine oxidase is irreversibly labelled with [3H]pargyline shows a distribution of enzyme similar to lysosomal acid phosphatase. After transplantation of reductively methylated 3H-labelled mitochondrial-outer-membrane vesicles the cells were treated with leupeptin to alter lysosomal density. This treatment leads to the predominant association of acid phosphatase with dense structures, whereas the 3H-labelled transplanted material predominantly does not change density. Therefore transplanted mitochondrial-outer-membrane proteins are found in intracellular vesicular structures from which the proteins are donated for destruction, at least in part, by a lysosomal mechanism.

scholarly journals Crystal structure of human monoamine oxidase B, a drug target enzyme monotopically inserted into the mitochondrial outer membrane

FEBS Letters ◽  
2004 ◽  
Vol 564 (3) ◽  
pp. 225-228 ◽  
Author(s):  
Claudia Binda ◽  
Frantisek Hubálek ◽  
Min Li ◽  
Dale E. Edmondson ◽  
Andrea Mattevi
Keyword(s):  
Crystal Structure ◽  
Monoamine Oxidase ◽  
Outer Membrane ◽  
Drug Target ◽  
Mitochondrial Outer Membrane ◽  
Monoamine Oxidase B ◽  
Target Enzyme

scholarly journals Degradation of transplanted rat liver mitochondrial-outer-membrane proteins in hepatoma cells

1983 ◽  
Vol 216 (1) ◽  
pp. 163-175 ◽  
Author(s):  
S M Russell ◽  
R J Mayer
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Monoamine Oxidase ◽  
Outer Membrane ◽  
Rat Liver ◽  
Outer Membrane Proteins ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Cell Protein ◽  
Mitochondrial Outer Membrane

Reductively [3H]methylated 3H mitochondrial-outer-membrane vesicles from rat liver and vesicles where monoamine oxidase has been derivatized irreversibly by [3H]-pargyline have been deliberately miscompartmentalized by heterologous transplantation into hepatoma (HTC) cells by poly(ethylene glycol)-mediated vesicle-cell fusion. Fluorescein-conjugated mitochondrial-outer-membrane vesicles have also been used to show that transplanted material is patched, capped and internalized. Reductively methylated outer-membrane proteins and monoamine oxidase are destroyed at the same rate (t1/2 24 h). Mitochondrial-outer-membrane proteins are not degraded at the same rate as HTC plasma-membrane proteins, endogenous cell protein, or endocytosed protein. Transplanted radiolabelled mitochondrial-outer-membrane proteins accumulate intracellularly in structures that are distinct from plasma membrane and lysosomes. However, when mitochondrial-outer-membrane vesicles derivatized with [14C]sucrose are transplanted, the acid-soluble degradation products accumulate in the lysosomal fraction. [14C]Sucrose-conjugated HTC cell plasma membrane accumulates in intracellular structures that are again distinct from plasma membrane and lysosomes. In contrast with the above observations, homologously transplanted mitochondrial-outer-membrane proteins from rat liver are destroyed in hepatocytes at rates that are remarkably similar (t1/2 60-70 h) to the rates in rat liver in vivo [Evans & Mayer (1982) Biochem. Biophys. Res. Commun. 107, 51-58].

A SEM and Light Microscope Study of the Epidermal Leaf Structures of the Carnivorous Plant, Sarracenia purpurea, L.

1971 ◽  
Vol 29 ◽  
pp. 358-359
Author(s):  
B. J. Panessa ◽  
J. F. Gennaro
Keyword(s):  
Methylene Blue ◽  
Toluidine Blue ◽  
Outer Surface ◽  
Microscope Study ◽  
Light Microscope ◽  
Carnivorous Plant ◽  
Sarracenia Purpurea ◽  
Inner Surface

Tissue from the hood and sarcophagus regions were fixed in 6% glutaraldehyde in 1 M.cacodylate buffer and washed in buffer. Tissue for SEM was partially dried, attached to aluminium targets with silver conducting paint, carbon-gold coated(100-500Å), and examined in a Kent Cambridge Stereoscan S4. Tissue for the light microscope was post fixed in 1% aqueous OsO4, dehydrated in acetone (4°C), embedded in Epon 812 and sectioned at ½u on a Sorvall MT 2 ultramicrotome. Cross and longitudinal sections were cut and stained with PAS, 0.5% toluidine blue and 1% azure II-methylene blue. Measurements were made from both SEM and Light micrographs.The tissue had two structurally distinct surfaces, an outer surface with small (225-500 µ) pubescent hairs (12/mm2), numerous stoma (77/mm2), and nectar glands(8/mm2); and an inner surface with large (784-1000 µ)stiff hairs(4/mm2), fewer stoma (46/mm2) and larger, more complex glands(16/mm2), presumably of a digestive nature.

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