The phosphate potential, adenylate energy charge and proton motive force in growing cells ofStreptococcus cremoris

✍ Scribed by R. Otto; B. Klont; B. Brink; W. N. Konings

• Publisher: Springer
• Year: 1984
• Tongue: English
• Weight: 742 KB
• Volume: 139
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00408376

✦ Synopsis

The phosphate potential (A G'p) and the proton motive force (Ap) were recorded simultaneously in Streptococcus cremoris under different conditions. If thermodynamic equilibrium exists the ratio A G'p/A p gives the number of protons translocated by the ATPase per ATP hydrolyzed or synthesized. In resting cells ATP-synthesis could be energized by a valinomycin-induced potassiumdiffusion potential. In the subsequent phase ATP-hydrolysis occurred and the A G'p/A p approached a value close to 2. In growing and fermenting cells the A G'p/Ap ratio was considerably higher (almost 5). This indicates that under growing conditions the A G'p is not near thermodynamic equilibrium with A p and that the membrane bound ATPase of S. cremoris acts exclusively as an ATP hydrolase. During logarithmic growth the phosphate potential, the A p and the adenylate energy charge remain essentially constant at -4 6 0 m V , -1 0 0 m V and 0.81, respectively. When the growth sustaining substrate is consumed a rapid dissipation of the phosphate potential to about -3 6 0 mV and of the A p to zero mV occurs.