Jul 9, 1976

Light-driven proton translocations in Halobacterium halobium

Biochimica Et Biophysica Acta
R A BogomolniW Stoeckenius


The purple membrane of Halobacterium halobium acts as a light-driven proton pump, ejecting protons from the cell interior into the medium and generating electrochemical proton gradient across the cell membrane. However, the type response of cells to light as measured with a pH electrode in the medium consists of an initial net inflow of protons which subsides and is then replaced by a net outflow which exponentially approaches a new lower steady state pH level. When the light turned off a small transient acidification occurs before the pH returns to the original dark level. We present experiments suggesting that the initial inflow of protons is triggered by the beginning ejection of protons through the purple membrane and that the initial inflow rate is larger than the continuing light-driven outflow. When the initial inflow has decreased exponentially to a small value, the outflow dominates and causes the net acidification of the medium. The initial inflow is apparently driven by a pre-existing electrochemical gradient across the membrane, which the cells can maintain for extended times in the absence of light and oxygen. Treatments which collapse this gradient such as addition of small concentrations of uncouplers abolish the...Continue Reading

  • References7
  • Citations38


  • References7
  • Citations38


Mentioned in this Paper

Physiologic Pulse
Uncoupling Agents
Adenosine Triphosphatases
ATP Synthesis Pathway
Carbonyl Cyanide m-Chlorophenyl Hydrazone
ATP12A gene
Acidification - ActCode

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