Energy Transduction in Anoxygenic Photosynthesis

Dutton, P. Leslie

doi:10.1007/978-3-642-70936-4_5

Cited by 27 publications

(32 citation statements)

References 76 publications

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“…Fractionation of the organic solvent extract prepared from proteinase K-treated spheroplasts and sequence analysis of peak fraction I (27) identical to a segment of the N-terminal region of the L chain of RC starting with position 16. Another major sequence in peak fraction I was Leu-Gly-Pro-Ile-Tyr-Leu-Gly-SerLeu .…”

Section: Resultsmentioning

confidence: 99%

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Localization of reaction center and B800-850 antenna pigment proteins in membranes of Rhodobacter sphaeroides

et al. 1988

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The localization of the N-and C-terminal regions of pigment-binding polypeptides of the bacterial photosynthetic apparatus of Rhodobacter sphaeroides was investigated by proteinase K treatment of chromatophore and spheroplast-derived vesicles and amino acid sequence determination. Under conditions of proteinase K treatment of chromatophores, which left the in vivo absorption spectrum and the membrane intact, 15 and 46 amino acyl residues from the N-terminal regions of the L and M subunits, respectively, of the reaction center polypeptides were removed. The N termini are therefore exposed on the cytoplasmic surface of the membrane. The C-terminal domain of the light-harvesting B800-850a and B870a polypeptides was found to be exposed on the periplasmic surface of the membrane. A total of 9 and 13 amino acyl residues were cleaved from the B800-850a and B870a polypeptides, respectively, when spheroplasts were treated with proteinase K. The N-terminal regions of the a polypeptides were not digested in either membrane preparation and were apparently protected from proteolytic attack. Seven N-terminal amino acyl residues of the B800-850,1 polypeptide were removed after the digestion of chromatophores. C-terminal residues were not removed after the digestion of chromatophores or spheroplasts. The C termini seem to be protected from protease attack by interaction with the membrane. Therefore, the N-terminal regions of the , polypeptides are exposed on the cytoplasmic membrane surface. The C termini of the B polypeptides are believed to point to the periplasmic space.The photosynthetic apparatus of Rhodobacter sphaeroides is located in an intracytoplasmic membrane system formed by invaginations of the cytoplasmic membrane (15). The major components of the photosynthetic apparatus are the light-harvesting (LH) or antenna pigment-protein complexes and the photochemical reaction center (RC), which are present as integral membrane particles (14). The absorption of light energy by LH complexes creates excited singlet states which migrate over the antennae downhill to the RC where they are trapped and converted into a membrane potential difference and a redox potential difference. This conversion drives a cyclic electron transport and the formation of a proton gradient across the membrane (16).The bacteriochlorophyll and carotenoid pigments are bound in stoichiometric ratios to the polypeptides of the three complexes: RC and the LH complexes B870 and B800-850, named according to their near-infrared absorption bands. In each LH complex, two different polypeptides bind noncovalently two or three bacteriochlorophyll and one or two carotenoid molecules. The axes of the pigment molecules have a strict orientation relative to the plane of the membrane (6, 18, 25). The pigment-binding polypeptides span the membrane once by a transmembrane a helix of hydrophobic amino acyl residues in LH complexes (5). The RC subunits M and L (RC-M and RC-L, respectively) span the membrane five times each (1,13,22,39). The N-and C-terminal domains of L...

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Section: Resultsmentioning

confidence: 99%

“…The absorption of light energy by LH complexes creates excited singlet states which migrate over the antennae downhill to the RC where they are trapped and converted into a membrane potential difference and a redox potential difference. This conversion drives a cyclic electron transport and the formation of a proton gradient across the membrane (16).…”

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confidence: 99%

Localization of reaction center and B800-850 antenna pigment proteins in membranes of Rhodobacter sphaeroides

et al. 1988

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“…The reduced sulfur compounds that primarily serve as substrates are oxidized and pyridine nucleotide (NAD ÷ in these organisms) are reduced by action of a NADH dehydrogenase enzyme. This membrane protein uses the energy of ATP (or the protonmotive force directly) to drive the otherwise thermodynamically unfavorable reduction of NAD ÷ and concomitant oxidation of the sulfur compound (Dutton 1986, Brune 1989.…”

Section: Mechanism Of Photosynthetic Energy Storagementioning

confidence: 99%

Origin and early evolution of photosynthesis

1992

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Photosynthesis was well-established on the earth at least 3.5 thousand million years ago, and it is widely believed that these ancient organisms had similar metabolic capabilities to modern cyanobacteria. This requires that development of two photosystems and the oxygen evolution capability occurred very early in the earth's history, and that a presumed phase of evolution involving non-oxygen evolving photosynthetic organisms took place even earlier. The evolutionary relationships of the reaction center complexes found in all the classes of currently existing organisms have been analyzed using sequence analysis and biophysical measurements. The results indicate that all reaction centers fall into two basic groups, those with pheophytin and a pair of quinones as early acceptors, and those with iron sulfur clusters as early acceptors. No simple linear branching evolutionary scheme can account for the distribution patterns of reaction centers in existing photosynthetic organisms, and lateral transfer of genetic information is considered as a likely possibility. Possible scenarios for the development of primitive reaction centers into the heterodimeric protein structures found in existing reaction centers and for the development of organisms with two linked photosystems are presented.

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“…After the quinone has been doubly reduced and has accepted two protons from nearby amino acid residues (Paddock et al 1989;Takabashi and Wraight 1990;Hanson et al 1992), it is released into the membrane. The proton uptake is associated with a proton gradient across the membrane that creates the driving force for the formation ofATP (Dutton 1986). …”

Section: Introductionmentioning

confidence: 99%

Comparative study of reaction centers from purple photosynthetic bacteria: Isolation and optical spectroscopy

Wang

Lin

et al. 1994

Photosynth Res

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Reaction centers from two species of purple bacteria, Rhodospirillum rubrum and Rhodospirillum centenum, have been characterized and compared to reaction centers from Rhodobacter sphaeroides and Rhodobacter capsulatus. The reaction centers purified from these four species can be divided into two classes according to the spectral characteristics of the primary donor. Reaction centers from one class have a donor optical band at a longer wavelength, 865 nm compared to 850 nm, and an optical absorption band associated with the oxidized donor at 1250 nm that has a larger oscillator strength than reaction centers from the second class. Under normal buffering conditions, reaction centers isolated from Rb. sphaeroides and Rs. rubrum exhibit characteristics of the first class while those from Rb. capsulatus and Rs. centenum exhibit characteristics of the second class. However, the reaction centers can be converted between the two groups by the addition of charged detergents. Thus, the observed spectral differences are not due to intrinsic differences between reaction centers but represent changes in the electronic structure of the donor due to interactions with the detergents as has been confirmed by recent ENDOR measurements (Rautter J, Lendzian F, Lubitz W, Wang S and Allen JP (1994) Biochemistry 33: 12077-12084). The oxidation midpoint potential for the donor has values of 445 mV, 475 mV, 480 mV and 495 mV for Rs. rubrum, Rs. centenum, Rb. capsulatus, and Rb. sphaeroides, respectively. Despite this range of values for the midpoint potential, the decay rates of the stimulated emission are all fast with values of 4.1 ps, 4.5 ps. 5.5 ps and 6.1 ps for quinone-reduced RCs from Rs. rubrum, Rb. capsulatus, Rs. centenum, and Rb. sphaeroides, respectively. The general spectral features of the initial charge separated state are essentially the same for the four species, except for differences in the wavelengths of the absorption changes due to the different donor band positions. The pH dependence of the charge recombination rates from the primary and secondary quinones differ for reaction centers from the four species indicating different interactions between the quinones and ionizable residues. A different mechanism for charge recombination from the secondary quinone, that probably is direct recombination, is proposed for RCs from Rs. centenum.

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Energy Transduction in Anoxygenic Photosynthesis

Cited by 27 publications

References 76 publications

Localization of reaction center and B800-850 antenna pigment proteins in membranes of Rhodobacter sphaeroides

Localization of reaction center and B800-850 antenna pigment proteins in membranes of Rhodobacter sphaeroides

Origin and early evolution of photosynthesis

Comparative study of reaction centers from purple photosynthetic bacteria: Isolation and optical spectroscopy

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