| Autor: |
Dracheva, Stella M., Drachev, Lel A., Zaberezhnaya, Svetlana M., Konstantincv, Alexander A., Semenov, Alexey Yu., Skulachev, Vladimir P. |
| Zdroj: |
FEBS Letters; September 1986, Vol. 205 Issue: 1 p41-46, 6p |
| Abstrakt: |
Redox, optical and kinetic characteristics of the four‐heme cytochrome ctightly bound to the reaction center complexes of Rhodopseudomonas viridishave been studied. The two high‐potential hemes, previously thought to be identical, are shown to differ in midpoint potentials, absorption spectra and kinetics of photooxidation. One heme is characterized by Em= 380 ± 10 mV, and a split α‐band (a peak at 559 nm and a shoulder at 553 nm) whereas the other has an Em= 310±10 mV and a symmetrical α‐band at 556 nm. Kinetics of laser flash oxidation of the c‐heme by the photogenerated P‐960+(τ ~ 0.3 μs) matches closely that of the bacteriochlorophyll reduction and precedes oxidation of the c‐556 heme, the latter occurring with τ ~ 2.5 μs concurrently with heme c‐re‐reduction. The data point to heme c‐being an immediate electron donor to P‐960+. Accordingly, this heme is tentatively identified with the iron‐porphyrin group proximal to the bacteriochlorophyll special pair in the three‐dimensional model of Rps. viridisreaction centers complexes [(1985) Nature 318, 618‐624]. Thus, the following reaction sequence is assumed: c‐556 → c‐559 → P‐960+. |
| Databáze: |
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