Spectral, redox and kinetic characteristics of high‐potential cytochrome c hemes in Rhodopseudomonas viridis reaction center

FEBS Letters

Dracheva, Stella M.¹  Skulachev, Vladimir P.¹  Semenov, Alexey Yu.¹  Drachev, Lel A.¹  Konstantincv, Alexander A.¹  Zaberezhnaya, Svetlana M.¹ 

[1] A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, Moscow 119899 USSR

关键词: (Rhodopseudomonas viridis);    Reaction center;    Multiheme cytochrome;    c Redoxpotential;    Rapid kinetics;    P-960 (BChl)2;    bacteriochlorophyll special pair;    RC;    reaction center complex;    LDAO;    lauryldimethylamine oxide;    Mops;    morpholinopropane sulfonic acid;   

DOI  :  10.1016/0014-5793(86)80862-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Redox, optical and kinetic characteristics of the four-heme cytochrome c tightly bound to the reaction center complexes of Rhodopseudomonas viridis have 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 E _m = 380 ± 10 mV, and a split α-band (a peak at 559 nm and a shoulder at 553 nm) whereas the other has an E _m = 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. viridis reaction centers complexes [(1985) Nature 318, 618-624]. Thus, the following reaction sequence is assumed: c-556 → c-559 → P-960⁺.

【 授权许可】

Unknown