Conversion of biomembrane-produced energy into electric form V. Membrane particles of Micrococcus lysodeikticus and pea chloroplasts

The formation of membrane potential in sonicated particles of an aerobic bacterium, Micrococcus lysodeikticus, and of pea chloroplasts has been demonstrated

To detect membrane potential, the responses of synthetic penetrating anions of phenyl dicarbaundecaborane (PCB⁻), tetraphenyl boron and anilinonaphthalene-sulfonate (ANS⁻) were studied. It was found that oxidation of NADH, succinate, malate, and lactate by oxygen in particles of M. lysodeikticus is coupled with anion uptake and ANS^- fluorescence enhancement, the fact testifying to the formation of membrane potential (“plus” inside particles). Uncouplers, cyanide and heptyl-hydroxyquinoline N-oxide prevent and reverse respiration-induced anion responses. Cyanide-resistant oxygen uptake is not coupled with ion fluxes. Ion responses are inhibited by acceptors competing with oxygen for electrons, such as Q₀, menadione, and also ferricyanide when malate or succinate (but not lactate) are oxidized. In cyanide-treated particles, reduction of ferricyanide by lactate, but not by malate, supports some anion transport. In contrast to respiration, ATP does not actuate ion fluxes in M. lysodeikticus particles competent in respiratory phosphorylation.

In sonicated particles of pea chloroplasts, light-induced anion uptake can be observed. Switching off light results in the efflux of anions accumulated on illumination. Again, ATP does not induce any anion response, although the system of photophosphorylation is active under the same conditions. It is concluded that formation of a membrane potential in particles of M. lysodeikticus and pea chloroplasts (plus inside) can be actuated by electron transfer but not ATP hydrolysis. The ineffectiveness of ATP seems to be a result of irreversibility, rather than damage, of the energy transfer chain; a property in which coupling mechanisms of M. lysodeikticus and chloroplasts differ from those of animal mitochondria and Rhodospirillum rubrum chromatophores.