Multichannel Flash Spectroscopy of the Reaction Centers of Wild-type and Mutant Rhodobacter sphaeroides: BacteriochlorophyllB-mediated Interaction Between the Carotenoid Triplet and the Special Pair¶†

2004 ◽  
Vol 79 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Juan B. Arellano ◽  
Thor Bernt Melø ◽  
Paul K. Fyfe ◽  
Richard J. Cogdell ◽  
K. Razi Naqvi
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Reaction Centers ◽  
Wild Type ◽  
Special Pair ◽  
Flash Spectroscopy

Lipids affect the charge stabilization in wild-type and mutant reaction centers of Rhodobacter sphaeroides R-26

1999 ◽  
Vol 26 (5) ◽  
pp. 465 ◽  
Author(s):  
László Nagy ◽  
Elfrida Fodor ◽  
Júlia Tandori ◽  
László Rinyu ◽  
Tibor Farkas
Keyword(s):  
Electron Transfer ◽  
Rhodobacter Sphaeroides ◽  
Electrostatic Interactions ◽  
Reaction Centers ◽  
Wild Type ◽  
Photosynthetic Membrane ◽  
Protein Ratio ◽  
Intracytoplasmic Membranes ◽  
In The Wild ◽  
Charge Stabilization

The effect of lipids on stabilization of electrons on the secondary quinone was studied in reaction centers (RC) of herbicide-sensitive and -resistant (L229Ile → Met) Rhodobacter sphaeroides R-26. The lipid concentration and the lipid/protein ratio of the intracytoplasmic membranes (ICM) were larger in the mutant RCs than in the wild-type. The free energy changes of Q A – Q B → Q A Q B – electron transfer were ΔG 0 = –57 meV, –69 meV, –85 meV for the wild-type and ΔG 0 = 0 meV, –15 meV, –46 meV for the mutant at pH = 8.0, in detergent, liposome and ICM, respectively. The differences in the stabilization energies of both strains decreased from the detergent via proteoliposome to chromatophore. We conclude that the energetics of the interquinone electron transfer depends on the environment of the reaction center. The steric and/or electrostatic interactions of the environment and Q B pocket can modulate the energetics of the charge stabilization over large distances. The interaction may have crucial importance on coupling the electron transport in the photosynthetic membrane to the anabolic/catabolic processes taking place in the cells.

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