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111.
The mechanism of excitation energy distribution between the two photosystems (state transitions) is studied in Synechocystis 6714 wild type and in wild type and a mutant lacking phycocyanin of Synechocystis 6803. (i) Measurements of fluorescence transients and spectra demonstrate that state transitions in these cyanobacteria are controlled by changes in the efficiency of energy transfer from PS II to PS I (spillover) rather than by changes in association of the phycobilisomes to PS II (mobile antenna model). (ii) Ultrastructural study (freeze-fracture) shows that in the mutant the alignment of the PS II associated EF particles is prevalent in state 1 while the conversion to state 2 results in randomization of the EF particle distribution, as already observed in the wild type (Olive et al. 1986). In the mutant, the distance between the EF particle rows is smaller than in the wild type, probably because of the reduced size of the phycobilisomes. Since a parallel increase of spillover is not observed we suggest that the probability of excitation transfer between PS II units and between PS II and PS I depends on the mutual orientation of the photosystems rather than on their distance. (iii) Measurements of the redox state of the plastoquinone pool in state 1 obtained by PS I illumination and in state 2 obtained by various treatments (darkness, anaerobiosis and starvation) show that the plastoquinone pool is oxidized in state 1 and reduced in state 2 except in starved cells where it is still oxidized. In the latter case, no important decrease of ATP was observed. Thus, we propose that in Synechocystis the primary control of the state transitions is the redox state of a component of the cytochrome b
6/f complex rather than that of the plastoquinone pool.Abbreviations DCCD
dicyclohexylcarbodiimide
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DBMIB
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone
- EF
exoplasmic face
- PQ
plasto-quinone
- PS
photosystem
- PBS
phycobilisome 相似文献
112.
The structure and arrangement of phycobilisomes of the unicellular red alga Porphyridium cruentum is compared with the organization of the thylakoid freeze-fracture particles in order to determine the relationship between phycobilisomes and photosystem II. The hemi-ellipsoidal phycobilisomes, 20 nm thick, are predominantly organized into rows; their centre to centre periodicity is 30–40 nm, so that they are well separated by a gap of 10–20 nm. The phycobilisomes are cleaved by a central faint furrow, parallel to the long axis from top to base. The organization of the exoplasmic particles in rows is similar to the arrangement of the phycobilisomes so that a structural relationship between both systems, previously demonstrated in cyanobacteria, is evident. Within the rows, the 10 nm EF-particles are grouped in tetrameric complexes separated by distances similar to those observed for phycobilisomes. We propose that the tetrameric EF-particle complexes correspond to tetrameric photosystem II complexes which bind one hemi-ellipsoidal phycobilisome on the stroma exposed surface of the thylakoid. A hypothetical model of this photosystem II-phycobilisome complex is presented. 相似文献
113.
Abstract: The cis elements mediating activation of the tyrosine hydroxylase gene by angiotensin II were examined by transfecting tyrosine hydroxylase promoter-luciferase constructs into cultured bovine adrenal medullary cells. Angiotensin II-responsive elements are located within −54/+25-bp and −269/−55-bp promoter regions and were identified, respectively, as cyclic AMP (CRE)- and 12- O -tetradecanoylphorbol 13-acetate responsive element (TRE)-like sequences. Unlike CRE, TRE also supports basal promoter activity. Mutations of TRE or CRE that reduced angiotensin II stimulation abolished in vitro binding of nuclear proteins to those elements, suggesting that proteins forming CRE- and TRE-inducible complexes may mediate angiotensin II stimulation. The TRE is adjacent to a dyad symmetry element. Those two sites form a common regulatory unit in which the dyad symmetry element acts as a repressor of the TRE site. Isolated dyad symmetry element did not bind nuclear proteins in vitro. In supercoiled DNA it exhibited S1 nuclease sensitivity and was recognized by a DNA cruciform-specific antibody consistent with the extrusion of a cruciform structure that overlaps with the TRE. A mutation that abolished formation of the cruciform correlated with a loss of repressor activity. We propose a novel model of tyrosine hydroxylase gene regulation in which functions of the TRE are modulated via structural transition in the adjacent DNA. 相似文献
114.
Böhm Manfred Lippoldt Andrea Wienen Wolfgang Ganten Detlev Bader Michael 《Molecular and cellular biochemistry》1996,163(1):217-221
TGR(mREN2)27 is a transgenic rat harboring the murine Ren-2 gene and exhibit fulminant hypertension and marked heart hypertrophy. In order to study the role of angiotensin II in the increase of cardiac mass, these animals were treated with anti-hypertensive and non-antihypertensive doses of the angiotensin II receptor AT1 antagonist Telmisartan for 9 weeks. All doses led to significant reductions of heart hypertrophy detected by the evaluation of the diameter of cardiac muscle bundles. We conclude from this study that cardiac hypertrophy in TGR(mREN2)27 is characterized by an increased volume of cardiomyocytes and an unchanged amount of fibrous tissue and that angiotensin II plays an important role in the mechanisms leading to this phenotype. 相似文献
115.
Ondrej Prasil Zbigniew Kolber Joseph A. Berry Paul G. Falkowski 《Photosynthesis research》1996,48(3):395-410
The oxygen flash yield (YO2) and photochemical yield of PS II (PS II) were simultaneously detected in intact Chlorella cells on a bare platinum oxygen rate electrode. The two yields were measured as a function of background irradiance in the steady-state and following a transition from light to darkness. During steady-state illumination at moderate irradiance levels, YO2 and PS II followed each other, suggesting a close coupling between the oxidation of water and QA reduction (Falkowski et al. (1988) Biochim. Biophys. Acta 933: 432–443). Following a light-to-dark transition, however, the relationship between QA reduction and the fraction of PS II reaction centers capable of evolving O2 became temporarily uncoupled. PS II recovered to the preillumination levels within 5–10 s, while the YO2 required up to 60 s to recover under aerobic conditions. The recovery of YO2 was independent of the redox state of QA, but was accompanied by a 30% increase in the functional absorption cross-section of PS II (PS II). The hysteresis between YO2 and the reduction of QA during the light-to-dark transition was dependent upon the reduction level of the plastoquinone pool and does not appear to be due to a direct radiative charge back-reaction, but rather is a consequence of a transient cyclic electron flow around PS II. The cycle is engaged in vivo only when the plastoquinone pool is reduced. Hence, the plastoquinone pool can act as a clutch that disconnects the oxygen evolution from photochemical charge separation in PS II.Abbreviations ADRY
acceleration of the deactivation reactions of the water-splitting enzyme (agents)
- Chl
chlorophyll
- cyt
cytochrome
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- FO
minimum fluorescence yield in the dark-adapted state
- FI
minimum fluorescence yield under ambient irradiance or during transition from the light-adapted state
- FM
maximum fluorescence yield in the dark-adapted state
- FM
maximum fluorescence yield under ambient irradiance or during transition from light-adapted state
- FV, FV
variable fluorescence (FV=FM–FO ; FV=FM–FI)
- FRR
fast repetition rate (fluorometer)
- PS II
quantum yield of QA reduction (PS II=(FM – FO)/FM or PS II)=(FM= – FI=)/FM=)
- LHCII
Chl a/b light harvesting complexes of Photosystem II
- OEC
oxygen evolving complex of PS II
- P680
reaction center chlorophyll of PS II
- PQ
plastoquinone
- POH2
plastoquinol
- PS I
Photosystem I
- PS II
Photosystem II
- RC II
reaction centers of Photosystem II
- PS II
the effective absorption cross-section of PHotosystem II
- TL
thermoluminescence
- YO2
oxygen flash yield
The US Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
116.
Electric field-induced charge recombination in Photosystem II (PS II) was studied in osmotically swollen spinach chloroplasts (blebs) by measurement of the concomitant chlorophyll luminescence emission (electroluminescence). A pronounced dependence on the redox state of the two-electron gate QB was observed and the earlier failure to detect it is explained. The influence of the QB/QB
– oscillation on electroluminescence was dependent on the redox state of the oxygen evolving complex; at times around one millisecond after flash illumination a large effect was observed in the states S2 and S3, but not in the state S4 (actually Z+S3). The presence of the oxidized secondary electron donor, tyrosine Z+, appeared to prevent expression of the QB/QB
– effect on electroluminescence, possibly because this effect is primarily due to a shift of the redox equilibrium between Z/Z+ and the oxygen evolving complex.Abbreviations BSA
bovine serum albumin
- EDTA
ethylene-diaminetetraacetic acid
- EL
electroluminescence
- FCCP
carbonylcyanide p-trifluoromethyloxyphenyl-hydrazone
- HEPESI
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- I
primary electron acceptor
- MOPS
3-(N-morpholino) propane sulfonic acid
- P680
primary electron donor of Photosystem II
- P700
primary electron donor of Photosystem I
- QA and QB
secondary and tertiary electron acceptors of Photosystem II
- Z
secondary electron donor (D1 Tyr 161) 相似文献
117.
Fifteen ancestral genotypes of United States soybean cultivars were screened for differences in photosynthetic electron transport capacity using isolated thylakoid membranes. Plants were grown in controlled environment chambers under high or low irradiance conditions. Thylakoid membranes were isolated from mature leaves. Photosynthetic electron transport was assayed as uncoupled Hill activity using 2,6-dichlorophenolindophenol (DCIP). Soybean electron transport activity was dependent on genotype and growth irradiance and ranged from 6 to 91 mmol DCIP reduced [mol chlorophyll]–1 s–1. Soybean plastocyanin pool size ranged from 0.1 to 1.3 mol plastocyanin [mol Photosystem I]–1. In contrast, barley and spinach electron transport activities were 140 and 170 mmol DCIP reduced [mol chlorophyll]–1 s–1, respectively, with plastocyanin pool sizes of 3 to 4 mol plastocyanin [mol Photosystem I]–1. No significant differences in the concentrations of Photosystem II, plastoquinone, cytochrome b6f complexes, or Photosystem I were observed. Thus, genetic differences in electron transport activity were correlated with plastocyanin pool size. The results suggested that plastocyanin pool size can vary significantly and may limit photosynthetic electron transport capacity in certain species such as soybean. Soybean plastocyanin consisted of two isoforms with apparent molecular masses of 14 and 11 kDa, whereas barley and spinach plastocyanins each consisted of single polypeptides of 8 and 12 kDa, respectively.Abbreviations DAP
days after planting
- DCIP
2,6-dichlorophenolindophenol
- LiDS
lithium dodecyl sulfate
- PPFD
photosynthetic photon flux density (mol photons m–2 s–1)
- PS I
Photosystem I
- PS II
Photosystem II
- P700
reaction center of Photosystem I
The US Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
118.
One of the fundamental discoveries of W. Arnold was the detection of thermally stimulated light emission from preilluminated photosynthetic material (Arnold and Sherwood (1957) Proc Natl Acad Sci USA 43: 105–114). This phenomenon, called thermoluminescence (TL), is characteristic of a wide range of materials (semiconductors, minerals, inorganic and organic crystals, and complex biological systems such as the photosynthetic apparatus) which share the common ability of storing radiant energy in thermally stabilized trap states.The original discovery of TL in dried chloroplasts later proved to be a phenomenon common to all photosynthetic organisms: photosynthetic bacteria, cyanobacteria, algae and higher plants. Following the pioneering work of Arnold, considerable effort has been devoted to identification and characterization of photosynthetic TL components. This work has firmly established the participation of various redox states of the water-oxidizing complex and the quinone electron acceptors of Photosystem II in the generation of photosynthetic glow curves. Since TL characteristics are very sensitive to subtle changes in redox properties of the involved electron transport components, the TL method has become a powerful tool in probing a wide range of PS II redox reactions. In this paper, we will review the impact of Arnold's work in initiating and promoting TL studies in photosynthesis and will cover the most important developments of this field of research until the present day.Abbreviations Chl
chlorophyll
- DL
delayed luminescence
- PS
photosystem
- TL
thermoluminescence 相似文献
119.
Thylakoids and Photosystem II particles prepared from the cyanobacterium Synechococcus PCC 7942 washed with a HEPES/glycerol buffer exhibited low rates of light-induced oxygen evolution. Addition of either Ca2+ or Mg2+ to both thylakoids and Photosystem II particles increased oxygen evolution independently, maximal rates being obtained by addition of both ions. If either preparation was washed with NaCl, light induced O2 evolution was completely inhibited, but re-activated in the same manner by Ca2+ and Mg2+ but to a lower level. In the presence of Mg2+, the reactivation of O2 evolution by Ca2+ allowed sigmoid kinetics, implying co-operative binding. The results are interpreted as indicating that not only Ca2+, but also Mg2+, is essential for light-induced oxygen evolution in thylakoids and Photosystem II particles from Synechococcus PC 7942. The significance of the reactivation kinetics is discussed. Reactivation by Ca2+ was inhibited by antibodies to mammalian calmodulin, indicating that the binding site in Photosystem II may be analogous to that of this protein.Abbreviation HEPES
n-2-Hydroxyethylpiperazine--2-ethane sulphonic acid 相似文献
120.
Li-Xin Zhang Hou-Guo Liang Jun Wang Wen-Rui Li Tian-Zhi Yu 《Photosynthesis research》1996,48(3):379-384
The 33 kDa protein of Photosystem II has one intrachain disulfide bond. Fluorescence spectroscopy shows that the major groups in the protein that bind to Ca2+ should be the carboxylic side groups of glutamic acid and/or aspartic acid. Fluorescence and Fourier-transform infrared (FTIR) spectroscopic studies indicate that the conformation of the 33 kDa protein is altered upon reduction, while the reduced protein still retains the secondary structure. FTIR spectroscopy also shows that the metal ions induce a relative decrease of unordered structure and -sheet, and a substantial increase of -helix in both the intact and the reduced 33 kDa protein. This indicates that the addition of cations results in a much more compact structure and that both the intact and the reduced 33 kDa proteins have the ability to bind calcium. The above results may suggest that the disulfide bridge is not essential for calcium binding.Abbreviations CD
circular dichroism
- FTIR
Fourier transform infrared
- La
lanthanum
- PS
photosystem
- Tb
terbium 相似文献