Article

Cation transport and metabolism in Streptococcus fecalis.

Biophysical Laboratory, Harvard Medical School, Boston, Mass. U.S.A.; Received 3 March 1966. Available online 3 February 2003.
Biochimica et Biophysica Acta (Impact Factor: 4.66). 11/1966; 126(2):308-20. DOI: 10.1016/0926-6585(66)90068-9
Source: PubMed

ABSTRACT 1.1. Streptococcus fecalis maintains an intracellular K+ concentration of 559 mM and an intracellular Na+ concentration of less than 5 mM when growing exponentially in a medium containing 4.6 mM K+ and 151 mM Na+. Cells harvested from the stationary phase are K+-poor and Na+-rich.2.2. An energy-dependent net uptake of K+ is observed following resuspension of K+-poor, Na+-rich cells in a neutral medium containing both substrate and K+.3.3. Net K+ uptake under these conditions is the result of two cation-exchange processes: (i) a K+−Na+ exchange which accounts for aapprox. 60% of the total K+ uptake; and, (ii) a K+−H+ exchange utilizing H+ present in the cell at the time of harvesting.4.4. Net cation transport is absolutely dependent on the metabolism of exogenous substrate, and both glucose and arginine will support the process, though at significantly different rates. With either substrate, the initial rate of net K+ uptake is equal to the calculated rate of ATP production.5.5. A transient two-fold increase in the glycolytic rate is closely associated with the onset of K+ uptake indicating a coupling between active cation transport and energy-yielding processes in this organism.

0 Bookmarks
 · 
23 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The rate of Na(+)/Na(+) exchange as measured with (24)Na(+) in Na(+)-rich cells of Chlorella pyrenoidosa is governed by a single rate constant and saturates with increasing external Na(+) concentration. The K mvalue for this process is 0.8 mM Na(+) and the maximum rate of exchange in illuminated cells is about 5 pmoles cm(-2) sec(-1). These values contrast with a K mof 0.18 mM K(+) and maximum rate of about 17 pmoles K(+)·cm(-2)·sec(-1) for net K(+) influx. Although the Na(+)/Na(+) exchange was only slightly sensitive to light it was inhibited by the uncouplers CCCP and DNP and by the energy transfer inhibitor DCCD. This inhibition of the rate of Na(+)/Na(+) exchange was not accompanied by a loss of internal Na(+). Both the effect of external K(+) on (24)Na(+) influx into Na(+)-rich cells and the inhibition of net K(+) uptake by the presence of external Na(+) indicates that Na(+)/Na(+) and K(+)/Na(+) exchanges share the same carrier and that the external site of this carrier has a three to four times higher affinity for K(+) over Na(+).
    Planta 03/1973; 111(1):13-22. · 3.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bacteria transduce and conserve energy at the plasma membrane in the form of an electrochemical gradient of hydrogen ions (deltap). Energized cells of Streptococcus lactis accumulate K+ ions presumably in exchange for H+. We reasoned that if the movement of H+ is limited, then an increase in H+ efflux, effected by potassium transport inward, should result in changes in the steady-state deltap. We determined the electrical gradient (deltapsi) from the fluorescence of a membrane potential-sensitive cyanine dye, and the chemical H+ gradient (deltapH) from the distribution of a weak acid. The deltap was also determined independently from the accumulation levels of the non-metabolizable sugar thiomethyl-beta-galactoside. KCl addition to cells fermenting glucose or arginine at pH 5 changed the deltap very little, but lowered the deltapsi, while increasing the deltapH. At pH 7, the deltapH only increased slightly; thus, the decrease in deltapsi, effected by addition of potassium ions, resulted in a lowered steady-state deltap. These effects were shown not to be due to swelling or shrinking of the cells. Thus, in these nongrowing cells, under conditions of energy utilization for the active transport of K+, the components of deltap can vary depending on the limitations on the net movement of protons.
    Journal of Bacteriology 07/1977; 130(3):1017-23. · 2.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Glycolyzing cells ofStreptococcus faecalis 9790 accumulate large amounts of lipid-soluble cations such as dimethyldibenzylammonium (DDA+). We showed in the preceding paper that uptake of DDA+ occurs in response to an electrical potential, interior negative, which arises by extrusion of H+ and Na+. The experiments described here deal with the mechanism of electrogenesis. Evidence is presented to indicate that extrusion of protons is an electrogenic, energy-linked process which can proceed against the electrochemical gradient for H+. Proton extrusion is blocked by dicyclohexylcarbodiimide (DCCD), an inhibitor of the membrane-bound ATPase ofS. faecalis. However, in a mutant whose ATPase is resistant to DCCD, proton extrusion is also resistant to the inhibitor. We conclude from these results that the membrane-bound ATPase is involved in proton extrusion. Extrusion of sodium can also occur against the electrochemical gradient, but we find no evidence for the existence of an electrogenic sodium pump. It rather appears, from studies with ionophorous agents and inhibitors of the ATPase, that the cells extrude Na+ in exchange for H+; the H+ is then extruded by the proton pump. Evidence is presented for an influx of H+ coupled to the efflux of Na+.Among the mutants known to be defective in K+ accumulation one class is deficient in proton extrusion and another lacks the Na+/H+ exchange. Thus, proton extrusion and Na+/H+ antiport are essential elements in K+ accumulation.
    Journal of Membrane Biology 11/1972; 8(1):45-62. · 2.17 Impact Factor