Energy transfer between the carotenoid and the bacteriochlorophyll within the B-800–850 light-harvesting pigment-protein complex of Rhodopseudomonas sphaeroides

Cogdell, Richard J.; Hipkins, M.F.; MacDonald, Wallace; Truscott, T. George

doi:10.1016/0005-2728(81)90138-9

Cited by 124 publications

(69 citation statements)

References 23 publications

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“…Our spectroscopic studies of the pigments (Fig. 2 and 3 (10) and to protect the photosynthetic apparatus from photooxidative damage which occurs in the presence of light and oxygen (11). Here we suggest that the increase in expression of the crtA gene in the BamHI H fragment as well as other crt genes by oxygen represents one type of protection by carotenoids from the potentially damaging effects of oxygen.…”

mentioning

confidence: 61%

Oxygen-regulated mRNAs for light-harvesting and reaction center complexes and for bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus during the shift from anaerobic to aerobic growth

Zhu¹,

Cook²,

Leach³

et al. 1986

J Bacteriol

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The stability and regulation by oxygen of mRNAs for the photosynthetic apparatus in Rhodobacter capsulatus have been studied by using proflavin to inhibit transcription and by shifting cells from anaerobic to aerobic conditions. The results from the inhibition experiments show that the mRNA for the light-harvesting LH-II polypeptides (,, a) is more stable than that for the light-harvesting LH-I polypeptides (0, a) during anaerobic growth, whereas the mRNAs for the reaction center polypeptides L (RC-L), M (RC-M), and H (RC-H) are less stable than both the LH-I and LH-II mRNAs. When photosynthetic cells are shifted from anaerobic to aerobic conditions, an immediate decrease in the levels of mRNA for the LH-I, LH-II, RC-L, RC-M, and RC-H proteins was observed. The level of mRNA for the LH-II proteins, however, is more sensitive to oxygen and is reduced faster than the level of mRNA for the LH-I proteins. These results suggest that oxygen represses the expression of genes coding for the light-harvesting antenna and reaction center complexes and may selectively accelerate the degradation of mRNA for the LH-II proteins. The mRNAs for several enzymes in the bacterioclhlorophyll biosynthetic pathway are regulated by oxygen in a similar manner. The mRNAs for carotenoid biosynthetic enzymes, however, are regulated by oxygen in a different way. We have found that the amounts of mRNAs for carotenoid biosynthetic enzymes, relative to the amounts of mRNAs for LH and RC, increased during the shift from anaerobic to aerobic conditions. We have particularly shown that although the expression of most photosynthetic genes in R. capsulatus is repressed by oxygen, the crtA gene, located in the BamHI H fragment of the R' plasmid pRPS404 and responsible for the oxidation of spheroidene to spheroidenone, responds to oxygen in an opposite fashion. This enzymatic oxidation may protect the photosynthetic apparatus from photooxidative damage.Rhodobacter capsulatus (19), which normally inhabits muddy lake bottoms and sewage lagoons, is a gram-negative, facultative, photosynthetic bacterium. It can generate metabolic energy by either aerobic respiration or anaerobic photosynthesis depending on the oxygen concentration and light intensity in its environment. The photosynthetic apparatus is composed of pigment-protein complexes for the conversion of light to chemical energy, including a shortwavelength light-harvesting antenna, LH-II (also denoted B800-850 by its near-infrared absorption maxima), a longwavelength light-harvesting antenna, LH-I (also denoted B870), and a reaction center complex consisting of three polypeptides (RC-L, RC-M, and RC-H). Each of these complexes binds bacteriochlorophyll and carotenoid pigments. The photosynthetic apparatus contains additional electron transport proteins to complete the cyclic pathway of electron transport. A decrease in oxygen concentration induces formation of the photosynthetic apparatus, which is localized within invaginations of the cellular membrane known as the intracytoplasmic membrane (16,...

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mentioning

confidence: 61%

Oxygen-regulated mRNAs for light-harvesting and reaction center complexes and for bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus during the shift from anaerobic to aerobic growth

Zhu¹,

Cook²,

Leach³

et al. 1986

J Bacteriol

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“…The fluorescence yield is 10% (32), and the triplet yield is Ϸ2% to 15% (42). The assembly is excited about once per 3 s with the source at 1 W. Thus there is a negligible probability for two singlet excitations being present in the ring at the same time.…”

Section: Discussionmentioning

confidence: 99%

Fluorescence and photobleaching dynamics of single light-harvesting complexes

Bopp

Jia

et al. 1997

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

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242

239

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Single light-harvesting complexes LH-2 from Rhodopseudomonas acidophila were immobilized on various charged surfaces under physiological conditions. Polarized light experiments showed that the complexes were situated on the surface as nearly upright cylinders. Their f luorescence lifetimes and photobleaching properties were obtained by using a confocal f luorescence microscope with picosecond time resolution. Initially all molecules f luoresced with a lifetime of 1 ؎ 0.2 ns, similar to the bulk value. The photobleaching of one bacteriochlorophyll molecule from the 18-member assembly caused the f luorescence to switch off completely, because of trapping of the mobile excitations by energy transfer. This process was linear in light intensity. On continued irradiation the f luorescence often reappeared, but all molecules did not show the same behavior. Some LH-2 complexes displayed a variation of their quantum yields that was attributed to photoinduced confinement of the excited states and thereby a diminution of the superradiance. Others showed much shorter lifetimes caused by excitation energy traps that are only Ϸ3% efficient. On repeated excitation some molecules entered a noisy state where the f luorescence switched on and off with a correlation time of Ϸ0.1 s. About 490 molecules were examined.

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“…sphueroides 2.4.1 (50,68,69) down to 30% for spirilloxanthin in the LHI complex of Rs. rubrum S1 (69); the energy transfer efficiencies were determined by the use of electronic-absorption and fluorescence spectra, which were normalized at the Q, absorption of BChl (50,69).…”

Section: Carotenoid-to-bchl Singlet-energy Transfermentioning

confidence: 98%

Singlet Excited States and the Light‐Harvesting Function of Carotenoids in Bacterial Photosynthesis

Koyama

Kuki

Andersson

et al. 1996

Photochem & Photobiology

196

210

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The recent results of stationary-state and time-resolved absorption, fluorescence and Raman spectroscopies of some typical carotenoids are summarized. Theoretical analyses of carotenoid singlet states and of carotenoidto-bacteriochlorophyll singlet-energy transfer are also included. On the bases of the energies, the lifetimes and other properties of singlet excited states of the carotenoids in solution and bound to the light-harvesting complexes, the energetics and the dynamics of the light-harvesting function in purple photosynthetic bacteria are discussed with emphasis on the 2A,-and B,+ states.

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Energy transfer between the carotenoid and the bacteriochlorophyll within the B-800–850 light-harvesting pigment-protein complex of Rhodopseudomonas sphaeroides

Cited by 124 publications

References 23 publications

Oxygen-regulated mRNAs for light-harvesting and reaction center complexes and for bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus during the shift from anaerobic to aerobic growth

Oxygen-regulated mRNAs for light-harvesting and reaction center complexes and for bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus during the shift from anaerobic to aerobic growth

Fluorescence and photobleaching dynamics of single light-harvesting complexes

Singlet Excited States and the Light‐Harvesting Function of Carotenoids in Bacterial Photosynthesis

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