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W Dubiel

Publications and source records attributed to W Dubiel.

68 records · Page 4Linked to original sources
PubMed1985

A mathematical model to study short-term regulation of mitochondrial energy transduction.

A mathematical model is presented which includes the following elementary process of mitochondrial energy transduction: hydrogen supply, proton translocation by the respiratory chain, proton-driven ATP synthesis by the F0F1-ATPase, passive back-flow of protons (leak) and carrier-mediated exchange of adenine nucleotides and phosphate. For these processes empirical rate laws are used. The model is applied to calculate time-dependent states of energy transduction in isolated rat liver mitochondria. From the general agreement of the computational results with experimental data (Ogawa, S. and Lee, T.M. (1984) J. Biol. Chem. 259, 10004-10011) the following conclusions can be drawn. (1) The length of the time interval during which mitochondria are able to maintain a relatively high and constant delta pH in the absence of oxygen (anaerobiosis) is limited by the availability of intramitochondrial ATP. (2) The overshoot kinetics of delta pH which appear when reoxigenating mitochondria after a preceeding anaerobiosis might be due to a lag phase kinetics of the F0F1-ATPase. (3) In phosphorylating mitochondria the homeostasis of delta pH is brought about by a high sensitivity of the respiration rate and the rate of the F0F1-ATPase as to changes of delta pH. (4) Analysis of the mean transient times shows that the rate of ATP synthesis in State 3 is controlled to almost the same extent by the hydrogen supply, the respiratory chain, the adenine nucleotide translocator and the proton leak.

Adenine Nucleotides↗
PubMed1985

Proteolysis of mitochondria in reticulocytes during maturation is ubiquitin-dependent and is accompanied by a high rate of ATP hydrolysis.

The ATP-dependent breakdown of mitochondria-containing stroma proceeds via the ubiquitin-requiring pathway. The proteolysis is linked to a large ATP-cleaved consumption amounting to 1 ATP per peptide bond or more. Proteins of mitochondria-containing stroma are much better substrates of ATP-ubiquitin-dependent proteolysis than heat-denatured ones. Hemin suppresses both proteolysis and ATP hydrolysis.

Adenosine Triphosphate↗
PubMed1984

Accounting for the ATP-consuming processes in rabbit reticulocytes.

The report deals with a detailed balance of ATP production and consumption of the rabbit reticulocyte. The sum-total of ATP produced amounts to 135 mmol . 1-1 . h-1. About 70% of the ATP consumption has been accounted for by specific processes. The main contributing processes are the globin synthesis with about 28%, the Na+, K+-ATPase with 23% and the proteolysis with more than 15%. 30% of ATP consumption has not been accounted for. Cycloheximide (20 microM) leads to a dissociation between synthesis and degradation of proteins, which argues against any obligatory connection between these processes. More than 90% of the lysine liberated from mitochondria by proteolysis were reutilized for the globin synthesis demonstrating the high nitrogen economy of reticulocytes. Each of the ATP-consuming processes studied appears to control ATP production in an independent manner without competition with each other.

Adenosine Triphosphate↗
PubMed1984

The effect of phenylhydrazine on protein breakdown in rabbit reticulocytes.

In contrast to reticulocytes produced by bleeding reticulocytes produced by injections of phenylhydrazine exhibit a sizeable Antimycin A- and a large salicylhydroxamic acid (SHAM)-resistant proteolysis. In their cytosol there exist both ATP-independent and ATP-dependent protease systems. The substrate of proteolysis are denatured and aggregated proteins arising from reactions of phenylhydrazine with cell constituents. In phenylhydrazine-induced reticulocytes there is an overlap between the basic biological process of maturation-dependent proteolysis of mitochondria and the breakdown of denatured and aggregated "abnormal" proteins.

Adenosine Triphosphate↗
PubMed1983

Calcium exerts an indirect effect on ATP-dependent proteolysis of rat liver mitochondria.

The ATP-dependent proteolysis of rat liver mitochondria prepared in electrolyte-poor sucrose media requires the presence of Ca2+. Lanthanum, an inhibitor of Ca2+ uptake, inhibits the proteolysis. In contrast, proteolysis of mitochondria prepared in a salt medium does not require Ca2+, nor is it inhibited by lanthanum. It is concluded that Caa+ exerts its effect in an indirect manner, by causing swelling and thereby increasing the accessibility of the membrane proteins of the inner mitochondrial membrane.

Adenosine Triphosphate↗
PubMed1983

Balance of ATP consumption of reticulocytes.

The sum-total of ATP produced amounts to 135 mmoles X 1 reticulocytes-1 X hour-1. About 70% of the ATP consumption has been accounted for by specific processes. The main contributing processes are: the globin synthesis with about 28%; the Na+/K+-ATPase with 23%, and the ATP-dependent share of proteolysis with more than 15%. 30% of ATP consumption has not been accounted for. Cycloheximide (20 X 10(-6) M) leads to a dissociation between synthesis and degradation of proteins, which argues against any obligatory connection between these processes. About 90% of the lysine liberated from mitochondria by proteolysis were reutilized for the globin synthesis demonstrating the high nitrogen economy of reticulocytes. Each of the ATP consuming processes studied appears to control ATP production in an independent manner without competition with each other.

Adenosine Triphosphate↗
PubMed1981

Determination and characteristics of energy-dependent proteolysis in rabbit reticulocytes.

In reticulocytes exists an extensive and time-limited ATP-dependent proteolysis which has been measured by a new method. This enzyme system attacks exclusively the mitochondria during the maturation of reticulocytes. The proteolysis is inhibited by anaerobiosis and salicylhydroxamic acid which indicates that it is preceded by the attack of lipoxygenase. There is some evidence for the universality of the ATP-dependent proteolysis, since liver mitochondria are also subject to it.

Adenosine Triphosphate↗
PubMed1980

Determination and characteristics of energy-dependent proteolysis in rabbit reticulocytes.

1. A method is reported, based on the isotopic dilution of lysine, which is suitable for the measurement of the degradation of stroma proteins of reticulocytes. 2. Proteolysis is extensive and time-limited. It may reach 50% of the stroma in 2 h at pH 7.6 and 37 degrees C. It is strongly dependent on pH and temperature, being small at low pH and temperatures. Proteolysis is largely ATP-dependent. The extent of proteolysis is nearly proportional to the degree of reticulocytosis. 3. The proteolytic system may be reconstructed in hemolysates if ATP is produced or supplied. It is assumed that the system is identical and that studied by Goldberg et al. and Hershko et al. on abnormal or denatured proteins as substrates. The main significance of the proteolytic system appears to be the degradation of mitochondria during maturation of the red cell.

Amino Acids↗
PubMedDate not supplied

Ubiquitin pathway: another link in the polyubiquitin chain?

Polyubiquitin has long been recognised as an intracellular signal. It now appears that different lysine linkages between the ubiquitin moieties are recognised as distinct signals and act in different cell processes. The generation of these different polyubiquitin chains may play an important part in the life of a cell.

Animals↗