pH‐jump‐induced phosphorylation of ADP in the cyanobacterium <i>Anacystis nidulans</i>

Muchl, R.; Peschek, Günter A.

doi:10.1016/0014-5793(83)80031-3

Cited by 8 publications

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“…Thus the data presented here indicate immediate coupling between electron transport and electrogenic proton extrusion in the plasma membrane of respiring A. nidulans. This does not exclude, of course, some proton-translocating ATPase enzymes in the same membrane (23); the existence of a reversible H+-ATPase in the plasma membrane of A. nidulans was recently inferred from net ATP formation in dark anaerobic cells to which an artificial pH gradient (19) or K+ diffusion potential (20) had been applied.…”

Section: Discussionmentioning

confidence: 99%

Transmembrane Proton Electrochemical Gradients in Dark Aerobic and Anaerobic Cells of the Cyanobacterium (Blue-Green Alga) Anacystis nidulans

Peschek

Czerny²,

Schmetterer³

et al. 1985

Plant Physiol.

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The transmembrane proton electrochemical potential gradient A;&H+ in whole cells of Anacystis nidulans was measured in aerobic and anaerobic dark conditions using the distribution, between external medium and cell interior, of radioactively labeled weak acids (acetylsalicyclic acid, 5,5-dimethyloxazolidine-2,4-dione) or bases (imidazole, methylamine), and permeant ions (tetraphenylphosphonium cation, thiocyanate anion), as determined by flow dialysis. Alternatively, the movements across the plasma membrane of ApH-indicating atebrin or 9-aminoacridine, and of A4-indicating 8-anilino-1-naphthalenesulfonate were qualitatively followed by fluorescence measurements. Attempts were made to discriminate between the individual chemiosmotic gradients across the cytoplasmic (plasmalemma) and the intracytoplasmic (thylakoid) membranes. By use of the ionophores nigericin, monensin, and valinomycin, the components of the proton motive force, namely the proton concentration gradient ApH and the electric membrane potential AA' were shown to be mutually exchangeable within the range of external pH values tested (3.2-11.0). Both components were depressed by the uncoupler carbonylcyanide mchlorophenylhydrazone, though inhibition of ApH was much more pronounced than that of A4', notably in the alkaline pH. range. The total proton electrochemical gradient across the plasma membrane was significantly higher in aerobic than in anaerobic cells and increased markedly (i.e. became more negative) towards lower pH. values. This increase was paralleled by a similar increase in the rate of endogenous respiration of the cells. At the same time the ATPase inhibitor dicyclohexylcarbodiimide only slightly affected the proton motive force across the plasma membrane of aerobic cells. The results will be discussed in terms of a respiratorily competent plasma membrane in Anacystis nidulans. plasma membranes of higher plant cells (4, 5). Fundamentally, the gradient incorporates two components, the proton concentration gradient (ApH) and the electric membrane potential (A+), AMH+ (mv) = AA -60 ApH (at 35C), which are bioenergetically equivalent and mutually exchangeable (3, 25).Chemiosmotic parameters have been studied in whole cells (8, 10, 30) and isolated thylakoid vesicles (24) of cyanobacteria, albeit with primary focus on photosynthetic energization of the membranes (see Peschek [27] for review). With respect to the chemiosmotic theory intact cyanobacteria are challenging experimental systems since these 'uncompartmentalized' prokaryotes nevertheless do contain two osmotically autonomous intracellular compartments, namely the cytoplasmic space (surrounded by the plasma membrane) and the intrathylakoid space (surrounded by the thylakoid membrane). Unfortunately, satisfactory biochemical separation and individual characterization of plasma and thylakoid membranes, respectively, has not yet been achieved with cyanobacteria. However, several independent lines of evidence have shown that, in A. nidulans, the plasma membrane contains a respir...

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Section: Discussionmentioning

confidence: 99%