The high potential iron‐sulfur protein (HiPIP) from <i>Rhodoferax fermentans</i> is competent in photosynthetic electron transfer

Hochkoeppler, Alejandro; Ciurli, Stefano; Venturoli, Giovanni; Zannoni, Davide

doi:10.1016/0014-5793(94)01334-w

Cited by 64 publications

(27 citation statements)

References 22 publications

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“…Another possibility is the existence of an electron donor other than soluble cytochrome c reducing the cytochrome subunit. HiPIP, a high-Era redox protein, may be one such element since it has been shown that HiPIP serves as an electron donor to the cytochrome subunit in R. gelatinosus TG-9 [21] and R. fermentans [22]. Figure 6 shows a lag-time in growth of approximately 4 h for the wild-type and 20 h for the C244 strain, subsequent to initial aerobic growth using residual oxygen.…”

Section: Resultsmentioning

confidence: 99%

Shortcut of the photosynthetic electron transfer in a mutant lacking the reaction center‐bound cytochrome subunit by gene disruption in a purple bacterium, Rubrivivax gelatinosus

1996

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A mutant lacking the reaction center-bound cytochrome subunit was constructed in a purple photosynthetic bacterium, Rubrivivax gelatinosus IL144, by inactivation of the cytochrome gene. Photosynthetic growth of the C244 mutant strain occurred at approximately half the rate of the wild-type strain. Although mutagenesis resulted in a greatly reduced amount of memhrane-bound cytochromes c, illumination induced cyclic electron transfer and the generation of membrane potential in the mutant as observed in the wild-type strain. These fmdings are consistent with previous observations that the cytochrome subunit is absent in the reaction center complex in some species of purple bacteria and that the biochemical removal of the subunit did not significantly affect the in vitro electron transfer from the soluble cytochrome c to the photosynthetic reaction center. These results suggest that the cytochrome subunit in purple bacteria is not essential for photosynthetic electron transfer and growth, even in those species generally containing the subunit.

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Section: Resultsmentioning

confidence: 99%

Shortcut of the photosynthetic electron transfer in a mutant lacking the reaction center‐bound cytochrome subunit by gene disruption in a purple bacterium, Rubrivivax gelatinosus

1996

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“…Although they have the right reduction potential (+90 to +450 mV) to couple bc1 and RC complexes (32), suggesting a role in cyclic photosynthetic electron transfer, their physiological function is still a matter for discussion. Earlier reports on the interaction between HiPIP and photosynthetic RC from Chromatium vinosum (35)(36)(37) and recent evidence suggesting that HiPIP is photooxidized by P+ in a fast (submillisecond) and a slow (millisecond) phase in Rf fermentans (29,38) support the concept that HiPIPs may play a role in the photocyclic electron transfer of purple bacteria. Evidence for the presence of a submillisecond electron transfer process was also recently reported in Rubrivivax gelatinosus (39).…”

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confidence: 78%

Kinetics of photo-induced electron transfer from high-potential iron-sulfur protein to the photosynthetic reaction center of the purple phototroph Rhodoferax fermentans.

Hochkoeppler

Zannoni

Ciurli

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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The kinetics of photo-induced electron transfer from high-potential iron-sulfur protein (HiPIP) to the photosynthetic reaction center (RC) of the purple phototroph Rhodoferaxfermentans were studied. The rapid photooxidation of heme c-556 belonging to RC is followed, in the presence of HiPIP, by a slower reduction having a second-order rate constant of4.8 x 107 M -l s -1. The limiting value of k.bs at high HiPIP concentration is 95 s-1. The amplitude of this slow process decreases with increasing HiPIP concentration. The amplitude of a faster phase, observed at 556 and 425 nm and involving heme c-556 reduction, increases proportionately. The rate constant of this fast phase, determined at 425 and 556 nm, is -3 x 105 s-1. This value is not dependent on HiPIP concentration, indicating that it is related to a first-order process. These observations are interpreted as evidence for the formation of a HiPIP-RC complex prior to the excitation flash, having a dissociation constant of -2.5 ,uM. The fast phase is absent at high ionic strength, indicating that the complex involves mainly electrostatic interactions. The ionic strength dependence of kobs for the slow phase yields a second-order rate constant at infinite ionic strength of 5.4 x 106 M-t.s-I and an electrostatic interaction energy of -2.1 kcal/mol (1 cal = 4.184 J). We conclude that Rhodoferax fermentans HiPIP is a very effective electron donor to the photosynthetic RC.Anoxygenic phototrophic bacteria contain two membranebound components that are essential for energy production, the photosynthetic reaction center (RC) and the cytochrome bc1 complex. Two types of RC have been structurally characterized: the RC from Rhodobacter sphaeroides is made of three subunits (1, 2), while, in addition to these, RC from Rhodopseudomonas viridis contains a fourth tetraheme cytochrome c subunit (2, 3). InRps. viridis the four heme groups have a bands at 559, 552, 556, and 554 nm, and reduction potentials of +380 mV, +20 mV, +310 mV, and -60 mV, respectively (4). The four hemes are arranged in an almost linear fashion, (2,5,6) and are aligned in the sequence P/c-559/c-552/c-556/c-554, where P indicates the bacteriochlorophyll special pair (4, 7). The highest potential heme (c-559) is oxidized the most rapidly (t/2 -300 ns) by the photooxidized P (P+), followed by a slower oxidation of heme c-556 (ti/2 2 ,us) (4,8,9). The quinol generated by RC photooxidation is utilized by the bc1 complex to reduce cytochrome c2 (10), a soluble protein closely related to mitochondrial cytochrome c (11,12). Cytochrome c2 then reduces the photooxidized RC, closing the photocycle. However, although cytochrome c2 reacts directly with P+ in Rb. sphaeroides (13-21), in Rps. viridis, it reacts with the tetraheme subunit (22-24). Only about half of the purple bacterial species described so far contain cytochrome c2 (25), and it is not known how the remaining species carry out electron transfer between the bc1 and RC complexes.The RC from the purple nonsulfur bacterium Rhodoferax fermentans (26)...

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“…On the basis of the measured redox potential of a HiPIP (0.345 V) from Rhodopseudomonas marina (23,47), the calculated iron couple Fe(OH) 3 -Fe 2ϩ (Ϫ1.1 V) (28) and the measured RC (0.4 to 0.5 V) in purple bacteria (57), a HiPIP is a reasonable candidate for this function because its redox potential falls between those of the iron couple and the RC. Spectroscopic and kinetic experiments have shown that HiPIPs can mediate electron transfer to the RC directly or via an RC-bound cytochrome in various purple bacteria (24,25,45,46,61). In this way, HiPIPs can functionally substitute for cytochrome c 2 , a common electron carrier in the periplasm of purple bacteria that shuttles electrons between the cytochrome bc1 complex and the RC during cyclic electron flow (47).…”

Section: Discussionmentioning

confidence: 99%

The pio Operon Is Essential for Phototrophic Fe(II) Oxidation in Rhodopseudomonas palustris TIE-1

2007

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The high potential iron‐sulfur protein (HiPIP) from Rhodoferax fermentans is competent in photosynthetic electron transfer

Cited by 64 publications

References 22 publications

Shortcut of the photosynthetic electron transfer in a mutant lacking the reaction center‐bound cytochrome subunit by gene disruption in a purple bacterium, Rubrivivax gelatinosus

Shortcut of the photosynthetic electron transfer in a mutant lacking the reaction center‐bound cytochrome subunit by gene disruption in a purple bacterium, Rubrivivax gelatinosus

Kinetics of photo-induced electron transfer from high-potential iron-sulfur protein to the photosynthetic reaction center of the purple phototroph Rhodoferax fermentans.

The pio Operon Is Essential for Phototrophic Fe(II) Oxidation in Rhodopseudomonas palustris TIE-1

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