+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Oxidation of cytochromes c and c2 by bacterial photosynthetic reaction centers in phospholipid vesicles. 1. Studies with neutral membranes



Oxidation of cytochromes c and c2 by bacterial photosynthetic reaction centers in phospholipid vesicles. 1. Studies with neutral membranes



Biochemistry 19(14): 3322-3327



The oxidation of cytochrome c2 by photosynthetic reaction center isolated from Rhodopseudomonas sphaeroides and incorporated into unilamellar phosphatidylcholine vesicles was found to be kinetically similar to that observed earlier for reaction centers in low detergent solution [Overfield, R.E., Wraight, C.A., & DeVault, D. (1979) FEBS Lett. 105, 137-142]. At low ionic strength the kinetics were biphasic. The fast phase indicated the formation of a cytochrome-reaction center complex with an apparent binding constant, KB, of about 10(5) M-1. However, KB decreased dramatically with increasing salt concentration, and no fast oxidation was detectable in 0.1 M NaCl. The slow cytochrome oxidation was first order in both cytochrome and reaction centers and, thus, second order overall. Deviations from theoretical second-order behavior were observed when the rate of the first-order back reaction of the primary photoproducts was significant compared to the cytochrome oxidation. This can cause serious overestimation of the second-order rate constant. The slow oxidation of cytochrome c2 by reaction centers in phosphatidylcholine vesicles exhibited a 40% lower encounter frequency than with the solubilized reaction center. This was attributed to the much lower diffusion coefficient of the reaction center in the vesicle membrane than in solution. No effects of diminished dimensionality were detected with neutral vesicles. An activation energy of 8.0 +/- 0.4 kcal x mol-1 was determined for the slow phase of cytochrome c2 oxidation by reaction centers in solution and in vesicles of several different phosphatidylcholines, including dimyristoylphosphatidylcholine above and below its phase transition temperature. Thus, the physical state of the lipid did not appear to affect any rate-limiting steps leading to cytochrome oxidation. The ionic strength dependence of the slow kinetics of oxidation of cytochromes c and c2 confirmed the electrostatic nature of the cytochrome-reaction center interaction, and the pH dependence indicated the titration of a group or groups, important to this interaction, at pH 9.5.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 043867422

Download citation: RISBibTeXText

PMID: 6250565

DOI: 10.1021/bi00555a034


Related references

Oxidation of cytochromes c and c2 by bacterial photosynthetic reaction centers in phospholipid vesicles. 2. Studies with negative membranes. Biochemistry 19(14): 3328-3334, 1980

Electron transfer and proton uptake of photosynthetic bacterial reaction centers reconstituted in phospholipid vesicles. Journal of Photochemistry & Photobiology B Biology 8(3): 263-278, 1991

Electron-conformation transitions in the complex of bacterial photosynthetic reaction centers with cytochromes. Biofizika 28(1): 9, 1983

Interactions of photosynthetic reaction centers and antenna proteins with phospholipid membranes. Biophysical Journal 49(2 Part 2): 487A, 1986

Evolutionary origins of the photosynthetic water oxidation cluster: bicarbonate permits Mn(2+) photo-oxidation by anoxygenic bacterial reaction centers. Chembiochem 14(14): 1725-1731, 2013

Electron transfer and proton uptake of photosynthetic bacterial reaction centres reconstituted in phospholipid vesicles. Journal of Photochemistry and Photobiology B: Biology 8(3): 263-277, 1991

On the nature of the hydrogen bonds to neutral ubiquinone in the QA binding site in purple bacterial photosynthetic reaction centers. Journal of Physical Chemistry. B 117(29): 8705-8713, 2013

Reaction centers from Rhodopseudomonas sphaeroides in reconstituted phospholipid vesicles. I. Structural studies. Journal of Bioenergetics and Biomembranes 19(3): 203-223, 1987

Orientation of the primary quinone of bacterial photosynthetic reaction centers contained in chromatophore and reconstituted membranes. Biochimica et Biophysica Acta 637(2): 278-290, 1981

Enthalpy/entropy driven activation of the first interquinone electron transfer in bacterial photosynthetic reaction centers embedded in vesicles of physiologically important phospholipids. Bioelectrochemistry 70(1): 18-22, 2007

Characterization of the primary electron donor p oxidation in bacterial photosynthetic reaction centers by redox triggered ir difference spectroscopy. Hester, R E And R B Girling (Ed ) Spectroscopy Of Biological Molecules; Fourth European Conference on The Spectroscopy Of Biological Molecules, York, England, Uk, September 1-6, Xxiii+464p Royal Society Of Chemistry: Cambridge, England, Uk Illus 75-76, 1991

Langmuir-Blodgett monolayer films of bacterial photosynthetic membranes and isolated reaction centers: preparation, spectrophotometric and electrochemical characterization. Biochimica et Biophysica Acta 1057(2): 239-257, 1991

X-ray diffraction studies on a crystalline bacterial photosynthetic reaction center: a progress report and conclusions on the structure of photosystem II reaction centers. Encyclopedia of plant physiology: New series9(19): 371-381, 1986

Oxidation reduction physical chemistry of the acceptor quinone complex in bacterial photosynthetic reaction centers evidence for a new model of herbicide activity. Israel Journal of Chemistry 21(4): 348-354, 1981

Q-Y-excitation resonance Raman studies of bacterial photosynthetic reaction centers. Biophysical Journal 64(2 Part 2): A215, 1993