PMID: 129328Feb 2, 1976

The control of the adenosine triphosphatase of Rhodospirillum rubrum chromatophores by divalent cations and the membrane high energy state

European Journal of Biochemistry
P A Edwards, J B Jackson

Abstract

1. The rate of ATP hydrolysis, catalysed by Rhodospirilum rubrum chromatophores is accelerated by low concentrations and inhibited by high concentrations of uncoupling agent. 2. The inhibition at high concentrations of uncoupling agent is potentiated by the presence of free magnesium ions. At low uncoupler concentrations magnesium has no effect on the rate of ATP hydrolysis. 3. Inhibition of ATP hydrolysis by high concentrations of uncoupling agent and free magnesium ions is reversed by illumination. Illumination has less effect at low magnesium concentrations. 4. Free calcium ions inhibit ATP hydrolysis independently of the coupled state of the membrane. 5. Under coupled conditions, magnesium ions can overcome the inhibition induced by calcium. The two ions complete for the same site on the enzyme. 6. Inhibition by free magnesium in highly uncoupled chromatophores and inhibition by free calcium are both non-competitive with respect to the divalent cation-ATP substrate. 7. These data are consistent with a model in which divalent cations can bind to a site on the enzyme which is distinct from the substrate site. The regulation of the enzyme activity by the high energy state of the membrane is dependent on the occupant of this site.

Citations

May 1, 1975·FEBS Letters·B C Johansson, M Baltscheffsky
Feb 22, 1973·Biochimica Et Biophysica Acta·R J van de StadtK van Dam
Oct 17, 1968·European Journal of Biochemistry·J B JacksonL V von Stedingk
Jul 26, 1963·Biochemical and Biophysical Research Communications·G HOCH, I MARTIN
Jun 1, 1960·Journal of General Microbiology·W R SISTROM

Related Concepts

Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone
Cations, Divalent
Calcium [EPC]
Energy Transfer
Magnesium Measurement
Calcium
Adenosine Triphosphatases
Darkness
Calcium ion
Bacterial Chromatophore

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