Energy transduction by the photosynthetic reaction center complex from Rhodopseudomonas viridis

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Abstract
Comparison of data of (i) the high‐resolution X‐ray analysis of the Rhodopseudomonas viridis reaction center complex and (ii) direct (with a voltmeter) measurement of charge displacement in the same complex is presented. It is revealed that 95% of the energy stored in the form of the membrane electric potential is due to electron and 5% to proton transfers. Five stages of the overall process were found to contribute to the light‐induced membrane charging, namely electron transfers from excited bacteriochlorophyll dimer to bacteriopheophytin, from bacteriopheophytin to MQ, from heme c‐559 to bacteriochlorophyll dimer, from heme c‐556 to heme c‐559 and H+ transfer from cytoplasmic water to the bound CoQ. The contribution of each stage to the energy storage depends upon the dielectric constant value in the respective part of the complex rather than upon the distance covered by the electron or proton. It appears to be higher, the deeper the redox groups involved are immersed into the membrane.

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