Unique relationships between the rates of oxidation and phosphorylation and the protonmotive force in rat-liver mitochondria.
The rate of ATP synthesis (JP) in isolated rat-liver mitochondria was strongly dependent on the magnitude of the protonmotive force (delta mu H+) across the mitochondrial inner membrane. Addition of different concentrations of various uncouplers or malonate to mitochondrial incubations in State 3 led to a depression of delta mu H+ and a concomitant decrease in JP. A unique relationship between JP and delta mu H+ was obtained, which was independent of the way in which delta mu H+ was varied. This unique relationship was observed when K+ (in the presence of valinomycin) was used as a probe for delta psi. Different relationships between JP and delta mu H+ were observed when K+ was used as a probe for delta psi and when K+ was measured after separation of the mitochondria by centrifugation without silicone oil. This led to a serious underestimation of delta psi, specifically when uncouplers were present, and non-unique flow-force relationships were thus obtained. Anomalous relationships between JP and delta mu H+ were also found when TPMP+ was used as a probe for delta psi. However, in uncoupler incubations the presence of TBP- strongly affected the TPMP+ accumulation ratio without any effect on the K+ accumulation or on JP and in the presence of TBP- unique relationships between JP and delta mu H+ were again obtained. This indicates that the accumulation of TPMP+ inside the mitochondria is not a straightforward function of delta psi but also depends on conditions like the presence of TBP- or uncouplers. We conclude that there is a unique relationship between the rate of phosphorylation and the protonmotive force in mitochondria and that under some conditions the behaviour of TPMP+ is anomalous.
Woelders
H
H
Laboratory of Biochemistry, University of Amsterdam, The Netherlands.
van der Velden
T
T
van Dam
K
K
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000502:physiology; D008564:Membrane Potentials; D008930:Mitochondria, Liver / Q000502:physiology*; D009861:Onium Compounds / Q000378:metabolism; D010085:Oxidative Phosphorylation; D011188:Potassium / Q000378:metabolism; D011522:Protons; D051381:Rats; D014320:Triphenylmethyl Compounds / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology
D009861:Onium Compounds; D011522:Protons; D014320:Triphenylmethyl Compounds; D014475:Uncoupling Agents; C011561:triphenylmethylphosphonium; D000255:Adenosine Triphosphate; D011188:Potassium