Photoinactivation of photophosphorylation and dark ATPase in Rhodospirillum rubrum chromatophores (original) (raw)
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Protein phosphorylation in chromatophores from Rhodospirillum rubrum
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1988
On incubation with [T-32p]ATP, a number of polypeptides of chromatophore and soluble fractions of Rhodospirillum rubrum are phosphorylated, including polypeptides of 70, 62, 61, 57, 49, 30, 22, 17, 13 and 10 kDa. Phosphorylation is stimulated by illumination and by addition of the oxidant potassium ferricyanide but is inhibited in the presence of the reductant, sodium dithionite. The electron-transport inhibitor, dibromomethylisopropylbenzoquinone (DBMIB), also inhibits light-stimulated protein phosphorylation. Phosphorylation of the 10 kDa polypeptide requires the readdition of a supernatant fraction to the membrane fraction. The data are compatible with a model we propose in which phosphorylation of B880 subunits is regulated by a component of the electron-transport chain in the vicinity of the ubiquinone pool.
Eur J Biochem. , 1977
Light-induced difference spectra between 400 and 640 nm of Rhodospirillum rubrum chromatophores were performed in the presence and absence of exogenous electron donor/acceptor systems and compared with the chemical oxidation spectrum. The results indicate that the component previously defined as P430 is not a unique entity but rather represents different species, or a mixture of species, under various conditions. Under all conditions in which the reaction center bacteriochlorophyll is reversibly photooxidized, as indicated by the bleaching around 600 nm, it is also contributing to the absorbance increase around 430 nm. In one case, in presence of reduced dichloroindophenol and in the absence of oxygen, the photooxidation of reaction center bacteriochlorophyll is fully supressed. Under these conditions an irreversible change around 430 nm is still observed and seems to be due to the Soret band of b-type cytochrome. In the presence of reduced dichloroindophenol and absence of oxygen there is a marked inhibition of photophosphorylation. This inhibition is apparently due to the complete reduction of the cyclic electron carriers. Addition of the low potential dye benzyl viologen facilitates an almost complete recovery of the reversible photooxidation of reaction center bacteriochlorophyll as well as of photophosphorylation. These results indicate that the apparent mid-point potential of the primary electron acceptor in Rhodospirillum rubrum chromatophores is probably in the range of that of benzyl viologen (E'o = - 340 mV).
Journal of Bioenergetics, 1975
Chromatophores of Rhodospirillum rubrum preilluminated in the presence of unlabelled phosphate form labelled ATP in the dark after being separated from the preincubation mixture by gel-filtration and incubated with ADP and 32P i. The driving force for the synthesis of this labelled ATP was previously shown to be ATP firmly bound to the membrane. The amount of labelled ATP produced is determined by measuring the incorporated 32P i and extrapolation of the values towards zero time incubation and is shown to correlate with the phosphoryIation activity of the chromatophores used. 2.5 nmoles ATP correspond to a phosphorylation activity of 100 Ltmoles ATP/mg Bchl. h. The results were compared with those from assays in which chromatophores were preincubated with pyrophosphate in the dark. The results strongly support the hypothesis that the X~ P formed in the light does not transfer its P to ADP in solution and therefore give further evidence to a double sited coupling factor as proposed previously.
Kinetics of the H+-ATPase in chromatophores from Rhodospirillum rubrum
FEBS Letters, 1985
The effect of the electrical potential on the H+-ATPase of Rhodospirillum rubrum is examined. It is shown that the forward reaction rate (ATP synthesis) is increased by a factor of 10 during illumination while the reversed rate is only slightly decreased. This indicates that the electrical potential across the membrane affects the rate constants mainly by increasing the forward rate constants rather than decreasing the reversed rate constants in order to go from net hydrolysis to net synthesis, Rhodospirillum rubrum
Photochemistry and Photobiology, 1966
THE DYE 5-methylphenazinium methyl sulfate (PMS) has been used either as an electron donor or as an electron acceptor in the respiratory This dye has also been used in the study of photosynthetic systems, acting as a bypass for the antimycin-A sensitive locus and as an agent which is capable of increasing rates of light induced phosphorylation under certain conditions.(3) Light induced reversible absorbancy and electron spin resonance (ESR) changes in both cell-free preparations and intact cells of photosynthetic bacteria have been observed and studied by several investigator~.(4-~~) We wish to report here some of our observa
Journal of Biological Chemistry
The Pi-ATP exchange and ATP hydrolytic reactions, by the F0F1 complex, were studied in Rhodospirillum rubrum chromatophores in the dark. An optimal pH between 7.0 and 8.5 was determined for the hydrolytic and exchange reactions. Under these conditions, the hydrolysis/exchange ratio was approximately 2. The kinetic analysis of the hydrolytic and exchange reactions using Mg-ATP as substrate showed a change in the hydrolysis/exchange ratio that varied between 2.0 and 2.8 as the substrate concentration was increased. With Ca-ATP, hydrolysis was not saturated up to a substrate concentration of 5.0 mM, and the hydrolysis/exchange ratios changed from 2 to 240 as the substrate concentration was increased from 0.06 to 5.0 mM. Free Mg2+ inhibited hydrolysis and phosphate uptake without altering the hydrolysis/exchange ratio. Nigericin induced an increase in the hydrolysis/exchange ratio from 2.7 to 130, whereas in the presence of valinomycin, this ratio increased from 2.7 to 21. From these re...