Biomaterial Database

Regulation of cyclic photophosphorylation in Rhodospirillum rubrum by the redox state of nicotinamide-adenine dinucleotide. 1979

G Gimenez-Gallego, and M P Ramirez-Ponce, and J M Ramirez

We have investigated the effect of the redox state of added NAD on the rates of anaerobic cyclic photophosphorylation which are supported by membrane vesicles isolated from Rhodospirillum rubrum. As the redox potential of NAD was lowered, the activity decreased according to a typical potentiometric titration. The Nernst plot showed an apparent midpoint potential (E'o) of -350 mV and had a slope which corresponded to a two-electron transition. Besides, an almost identical potentiometric relationship was found to exist between the extent of light-elicited ATP formation in anaerobic suspensions of intact R. rubrum cells and the redox potential of intracellular NAD. These results suggest that physiological photophosphorylation in R. rubrum requires the oxidized form of a membrane-bound constituent (E'o = -350 mV) whose redox state is controlled by the redox state of cytoplasmic NAD.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D009243	NAD	A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). (Dorland, 27th ed)	Coenzyme I,DPN,Diphosphopyridine Nucleotide,Nadide,Nicotinamide-Adenine Dinucleotide,Dihydronicotinamide Adenine Dinucleotide,NADH,Adenine Dinucleotide, Dihydronicotinamide,Dinucleotide, Dihydronicotinamide Adenine,Dinucleotide, Nicotinamide-Adenine,Nicotinamide Adenine Dinucleotide,Nucleotide, Diphosphopyridine
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010785	Photophosphorylation	The use of light to convert ADP to ATP without the concomitant reduction of dioxygen to water as occurs during OXIDATIVE PHOSPHORYLATION in MITOCHONDRIA.	Photosynthetic Phosphorylation,Phosphorylation, Photosynthetic,Phosphorylations, Photosynthetic,Photophosphorylations,Photosynthetic Phosphorylations
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D000693	Anaerobiosis	The complete absence, or (loosely) the paucity, of gaseous or dissolved elemental oxygen in a given place or environment. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)	Anaerobic Metabolism,Anaerobic Metabolisms,Anaerobioses,Metabolism, Anaerobic,Metabolisms, Anaerobic
D012247	Rhodospirillum rubrum	Vibrio- to spiral-shaped phototrophic bacteria found in stagnant water and mud exposed to light.