The electrochemical H+ gradient in the yeastRhodotorula glutinis |
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Authors: | Milan Höfer Klaas Nicolay George Robillard |
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Institution: | (1) Botanisches Institut der Universität Bonn, Kirschalle 1, 5300 Bonn, Germany;(2) Laboratory of Physical Chemistry, University of Groningen, Nijenborgh 16, 9747 AG Groningen, The Netherlands;(3) Present address: Biochemical Laboratory, University of Utrecht, Padualaan 8, 3508 TB Utrecht, The Netherlands |
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Abstract: | The electrochemical gradient of protons,
, was estimated in the obligatory aerobic yeastRhodotorula glutinis in the pH0 range from 3 to 8.5. The membrane potential, , was measured by steady-state distribution of the hydrophobic ions, tetraphenylphosphonium (TPP+) for negative above pH0 4.5, and thiocyanate (SCN–) for positive below pH0 4.5. The chemical gradient of H+ was determined by measuring the chemical shift of intracellular Pi by31P-NMR at given pH0 values. The values of pHi increased almost linearly from 7.3 at pH0 3 to 7.8 at pH0 8.5. In the physiological pH0 range from 3.5 to 6,
was fairly constant at values between 17–18 KJ mol–1, gradually decreasing at pH0 above 6. In deenergized cells, the intracellular pHi decreased to values as low as 6, regardless of whether the cell suspension was buffered at pH0 4.5 or 7.5. There was no membrane potential detectable in deenergized cells. |
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Keywords: | Electrochemical H+-gradient intracellular pHi membrane potential nuclear magnetic resonance electrogenic transport transport in yeast Rhodotorula glutinis |
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