scholarly journals Action of chlorpromazine. 3. Mitochondrial adenosine triphosphatase and the adenosine triphosphate–adenosine diphosphate exchange*

1960 ◽  
Vol 76 (1) ◽  
pp. 200-205 ◽  
Author(s):  
M. J. R. Dawkins ◽  
J. D. Judah ◽  
K. R. Rees
Keyword(s):  
Adenosine Triphosphate ◽  
Adenosine Triphosphatase ◽  
Adenosine Diphosphate

scholarly journals Flexibility of an Active Center in Sodium-Plus-Potassium Adenosine Triphosphatase

1969 ◽  
Vol 54 (1) ◽  
pp. 306-326 ◽  
Author(s):  
R. L. Post ◽  
S. Kume ◽  
T. Tobin ◽  
B. Orcutt ◽  
A. K. Sen
Keyword(s):  
Active Center ◽  
Adenosine Triphosphate ◽  
Adenosine Triphosphatase ◽  
Plasma Membranes ◽  
Adenosine Diphosphate ◽  
Ion Concentration ◽  
Potassium Ions ◽  
Sodium Ions ◽  
Intact Cells ◽  
Electrophoretic Patterns

In plasma membranes of intact cells an enzymatic pump actively transports sodium ions inward and potassium ions outward. In preparations of broken membranes it appears as an adenosine triphosphatase dependent on magnesium, sodium, and potassium ions together. In this adenosine triphosphatase a phosphorylated intermediate is formed from adenosine triphosphate in the presence of sodium ions and is hydrolyzed with the addition of potassium ions. The normal intermediate was not split by adenosine diphosphate. However, selective poisoning by N-ethylmaleimide or partial inhibition by a low magnesium ion concentration yielded an intermediate split by adenosine diphosphate and insensitive to potassium ions. Pulse experiments on the native enzyme supported further a hypothesis of a sequence of phosphorylated forms, the first being made reversibly from adenosine triphosphate in the presence of sodium ion and the second being made irreversiblyfrom the first and hydrolyzed in the presence of potassium ion. The cardioactive steriod inhibitor, ouabain, appeared to combine preferentially with the second form. Phosphorylation was at the same active site according to electrophoretic patterns of proteolytic phosphorylated fragments of both reactive forms. It is concluded that there is a conformational change in the active center for phosphorylation during the normal reaction sequence. This change may be linked to one required theoretically for active translocation of ions across the cell membrane.

scholarly journals Altered chemomechanical coupling causes impaired motility of the kinesin-4 motors KIF27 and KIF7

2018 ◽  
Vol 217 (4) ◽  
pp. 1319-1334 ◽  
Author(s):  
Yang Yue ◽  
T. Lynne Blasius ◽  
Stephanie Zhang ◽  
Shashank Jariwala ◽  
Benjamin Walker ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Cell Division ◽  
Adenosine Triphosphate ◽  
Adenosine Triphosphatase ◽  
Adenosine Diphosphate ◽  
Microtubule Dynamics ◽  
Microtubule Organization ◽  
High Affinity ◽  
Chemomechanical Coupling ◽  
Mechanistic Basis

Kinesin-4 motors play important roles in cell division, microtubule organization, and signaling. Understanding how motors perform their functions requires an understanding of their mechanochemical and motility properties. We demonstrate that KIF27 can influence microtubule dynamics, suggesting a conserved function in microtubule organization across the kinesin-4 family. However, kinesin-4 motors display dramatically different motility characteristics: KIF4 and KIF21 motors are fast and processive, KIF7 and its Drosophila melanogaster homologue Costal2 (Cos2) are immotile, and KIF27 is slow and processive. Neither KIF7 nor KIF27 can cooperate for fast processive transport when working in teams. The mechanistic basis of immotile KIF7 behavior arises from an inability to release adenosine diphosphate in response to microtubule binding, whereas slow processive KIF27 behavior arises from a slow adenosine triphosphatase rate and a high affinity for both adenosine triphosphate and microtubules. We suggest that evolutionarily selected sequence differences enable immotile KIF7 and Cos2 motors to function not as transporters but as microtubule-based tethers of signaling complexes.

Studies on the mechanism of action of ethylene. II. Effects of ethylene on mitochondria from rat liver and yeast, and on mitochondrial adenosine triphosphatase

1968 ◽  
Vol 46 (3) ◽  
pp. 283-288 ◽  
Author(s):  
A. O. Olson ◽  
Mary Spencer
Keyword(s):  
Adenosine Triphosphate ◽  
Rat Liver ◽  
Mechanism Of Action ◽  
Mitochondrial Membrane ◽  
Adenosine Triphosphatase ◽  
Adenosine Diphosphate ◽  
Yeast Mitochondria ◽  
Mitochondrial Volume ◽  
High Concentrations

Ethylene treatment of rat liver and yeast mitochondria was found to increase the rate of mitochondrial volume change caused by adenosine diphosphate or adenosine triphosphate. As well, ethylene increased the rate of adenosine triphosphate hydrolysis by mitochondria from rat liver, yeast, and bean cotyledons. However, the gas had no effect on the reactivity of a partially purified adenosine triphosphatase prepared from mitochondria of rat liver or bean cotyledon. For ethylene to exert its effect, it appears that the enzyme must be in its natural locale in the mitochondrial membrane, where the gas can accumulate in relatively high concentrations. The effects of ethylene on respiration in vivo are explicable on the basis of these observations.

Studies on the mechanism of action of ethylene. I. The effects of ethylene on mitochondria prepared from bean cotyledons

1968 ◽  
Vol 46 (3) ◽  
pp. 277-282 ◽  
Author(s):  
A. O. Olson ◽  
Mary Spencer
Keyword(s):  
Adenosine Triphosphate ◽  
Mechanism Of Action ◽  
Volume Change ◽  
Calcium Ions ◽  
Adenosine Triphosphatase ◽  
Respiratory Control ◽  
Adenosine Diphosphate ◽  
Volume Changes ◽  
Ethylene Treatment ◽  
Mitochondrial Volume

For investigations of the possible mechanism of action of ethylene, intact mitochondria with respiratory control were prepared from bean cotyledons of various ages. Ethylene treatment resulted in an increase in the rate of mitochondrial volume change caused by adenosine diphosphate or adenosine triphosphate, but was without effect on spontaneous changes or those mediated by phosphate or calcium ions. This suggested that ethylene affects an enzyme with which the nucleotides react and which is associated with mitochondrial volume changes. Such an enzyme is mitochondrial adenosine triphosphatase, and it was found that ouabain, known to be an inhibitor of this enzyme in some cotyledons, prevented the response to ethylene.

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