共查询到20条相似文献,搜索用时 31 毫秒
1.
Götz Harnischfeger 《BBA》1978,503(3):473-479
4-Phenylspiro[furan-2(3H),1-phtalan]3,3′-dione (fluorescamine) was used to covalently modify amino groups of thylakoids. Subsequently its effect on parameters of energy transfer and phosphorylating activity was assessed. While electron transport, the extent of proton uptake, 515 nm change and 9-aminoacridine quench were relatively resistant to such treatment, the functions connected to coupling factor 1, namely ATP formation by acid/base transition, ATPase activity and photophosphorylation were affected much earlier. Photophosphorylation appears to be the most sensitive. The data are interpreted as indicating an involvement of free amino groups in energy transfer. 相似文献
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The interaction of tentoxin with solubilized lettuce chloroplast coupling factor 1 was characterized by direct binding studies, measurement of the time course of ATPase inhibition, and steady-state enzyme kinetics. Neither substrates, products or Ca2+ competed with the tentoxin binding site, nor did they induce any large change in tentoxin affinity. The inhibition of lettuce chloroplast coupling factor 1 ATPase was found to be the time dependent, and at equilibrium the affinities estimated by equilibrium ultrafiltration and enzyme inhibition were similar (1.8 · 108M?1). The steady-state kinetics best fit an uncompetitive pattern suggesting that the inhibited steps follow an irreversible step occurring after ATP binding. 相似文献
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Tentoxin at 10–1000 μM causes a marked species-selective stimulation of coupling factor 1 Ca2+-dependent ATPase activity (Ka 6.3 · 103 M?1). This effect decreases the Km for ATP to about 0.3 mM and increases V 2.75-fold. Above 1.6 μM tentoxin the rate of coupled electron transport was reduced to basal without uncoupling. 相似文献
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Bovine heart submitochondrial particles depleted of F1 by treatment with urea (‘F1-depleted particles’) were incubated with soluble F1-ATPase. The binding of F1 to the particles and the concomitant conferral of oligomycin sensitivity on the ATPase activity required the presence of cations in the incubation medium. NH+4, K+, Rb+, Cs+, Na+ and Li+ promoted reconstitution maximally at 40–74 mM, guanidinium+ and Tris+ at 20–30 mM, and Ca2+ and Mg2+ at 3–5 mM. The particles exhibited a negative ζ-potential, as determined by microelectrophoresis, and this was neutralized by mono- and divalent cations in the same concentration range as that needed to promote F1 binding and reconstitution of oligomycin-sensitive ATPase. It is concluded that the cations act by neutralizing negative charges on the membrane surface, mainly negatively charged phospholipids. These results are discussed in relation to earlier findings reported in the literature with F1-depleted thylakoid membranes and with submitochondrial particles depleted of both F1 and the coupling proteins F6 and oligomycin sensitivity-conferring protein. 相似文献
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The rate of ATP synthesis of illuminated chloroplasts is correlated with the electric conductance of their inner membranes. In agreement with previous studies it is shown that ATP synthesis is paralleled by an increased conductance of the thylakoid membrane. This conductance together with the ability to form ATP is abolished if chloroplasts are treated with an antibody against the coupling factor CF1. It is not influenced by the fragmented monovalent antibody. This parallels the lack of influence of the fragmented antibody on ATP synthesis in contrast to its influence on hydrolysis and exchange reactions. We conclude that there are different sites for the interaction of the coupling factor with adenine nucleotides.Extraction of the coupling factor is shown to increase the membrane conductance by more than two orders of magnitude. Reincorporation of the crude coupling factor partially restores the net conductance of the membrane (increase in resistance by a factor of 2.5), while a higher degree of restoration was observed for ATP synthesis and the proton conductivity of the membrane. We conclude that the extraction procedure opens different conductive channels in the membrane; a proton specific one, possibly associated with the binding protein for the coupling factor, plus other channels for “non-protons” which in contrast to the proton channel cannot be plugged by reincorporation of the coupling factor. 相似文献
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黄卓辉 《植物生理与分子生物学学报》1986,(2)
在不外加Mg~(2 )的条件下,激活液中加入30 mMNaCl或15 mM KCl,能促进叶绿体膜上偶联因子的腺三磷酶活力。其促进程度与叶绿素浓度、反应底物ATP浓度及DTT的存在有关。但此促进现象可被加入低浓度的EDTA所消除,NaCl及KCl可将叶绿体内含有的内源或结合态的Mg~(2 )释放出来,有活化腺三磷酶的作用。 相似文献
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The binding of various nucleotides to chloroplast coupling factor CF1 was studied by two dialysis techniques. It was found that the number of nucleoside diphosphate sites and their specificities for the base moiety is dependent on the magnesium concentration. In the presence of 50 μM added MgCl2, the protein has a single strong site/mol protein with Kd = 0.5 μM for ADP and high specificity (Kd > 20 μM for ?ADP, GDP, CDP). In the presence of 5 mM MgCl2, the protein has two independent tight ADP sites (Kd = 0.4 μM) of low specificity (Kd ≈ 0.8, 2, and 2 μrmM, respectively for ?ADP, GDP, and CDP). These results are compared with the specificity of the partial reactions for photophosphorylation. 相似文献
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A group of 12 alkaloids were tested as inhibitors of photophosphorylation in spinach chloroplasts. Ajmaline, a dihydroindole alkaloid, was found to be the strongest inhibitor of both cyclic and non-cyclic photophosphorylation. Low concentrations of ajmaline also inhibited the dark and light ATPases, and the coupled electron flow from water to ferricyanide, measured either as ferrocyanide formed or as oxygen evolved, but not the uncoupled electron transport or the pH rise of illuminated unbuffered suspensions of chloroplasts. Higher concentrations of ajmaline stimulated, instead of inhibiting, photosynthetic electron transport or oxygen evolution and decreased the pH rise, thus behaving as an uncoupler, such as ammonia.Photophosphorylation was partially inhibited by 100 μM dihydrosanguinarine, 100 μM dihydrochelerythrine (benzophenanthridine alkaloids); 500 μM O,O'-dimethylmagnoflorine, 500 μM N-methylcorydine (aporphine alkaloids) and 1 mM julocrotine. They also inhibited coupled oxygen evolution and only partially (dihydrosanguinarine and dihydrochelerythrine) or not at all (the other alkaloids) uncoupled oxygen evolution.Spegazzinine (dihydroindole alkaloid), magnoflorine, N-methylisocorydine, coryneine (aporphine alkaloids), candicine and ribalinium chloride were without effect on photophosphorylation at 500 μM. 相似文献
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The membrane bound coupling factor of photophosphorylation is studied after pretreatment of broken chloroplasts with the bifunctional N,N-orthophenyldimaleimide under energization of the thylakoid membrane by mild flashing light. The proton conduction of the membrane is monitored both via the electrochromic absorption changes and via selective pH-indicating dyes. It is found that the coupling factor, after interaction with N,N-orthophenyldimaleimide during the preillumination period, shortcircuits one of the two protons pumped inside after excitation of chloroplasts with one short flash of light. In contrast to the low proton conductivity of the unperturbed thylakoid membrane (relaxation time for a proton gradient > 5s), this extra proton channel leads to a partial relaxation of a proton gradient within a few ms. Although limited to only one proton per electron, this extra proton conducting pathway is not otherwise specific. It operates with protons resulting from both Photosystem I and Photosystem II activity. In addition it operates with protons already present in the internal phase before firing of the exciting light flash. These effects are prevented by the presence of ATP (but not GTP) during the preillumination period. It is suggested that the modified coupling factor is gated open by the light induced electric field across the thylakoid membrane while self closing after passage of one proton per activated coupling factor. 相似文献
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The ATPase activity of the chloroplast coupling factor 1 (CF1) isolated from the green alga Dunaliella is completely latent. A brief heat treatment irreversibly induces a Ca2+ -dependent activity. The Ca2+ dependent ATPase activity can be reversibly inhibited by ethanol, which changes the divalent cation dependency from Ca2+ to Mg2+. Both the Ca2+ -dependent and Mg2+ -dependent ATPase activities of heat-treated Dunaliella CF1 are inhibited by monospecific antisera directed against Chlamydomonas reinhardi CF1. However, when assayed under identical conditions, the Ca2+ -dependent ATPase activity is significantly more sensitive to inhibition by the antisera than is the Mg2+ -dependent activity. These data are interpreted as indicating that soluble Dunaliella CF1 can exist in a variety of conformations, at least one of which catalyzes a Ca2+ -dependent ATPase and two or more of which catalyze an Mg2+ -dependent ATPase. 相似文献
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Quercetin, an energy transfer inhibitor in photophosphorylation 总被引:1,自引:0,他引:1
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叶片预照光对光合磷酸化和电子传递偶联效率的促进作用 总被引:1,自引:0,他引:1
魏家绵 《植物生理与分子生物学学报》1986,(2)
菠菜叶片经预照光处理后提取的叶绿体,不但光合磷酸化活力增加,而且偶联效率P/O也提高,其提高P/O的作用与多粘菌素的作用不能叠加,叶片预照光可能通过使偶联因子产生漏能减少的变构而提高p/O的。用两阶段光合磷酸化法测得叶片预照光,在促进光合磷酸化时也能促进高能态积累。用CF_1抗体,NEM和五羟黄酮等处理叶绿体的研究表明,叶片预照光引起CF_1的构象变化——γ,亚单位上的SH基内埋而α.β亚单位上的催化中心却更加暴露。活体中的P/O值也许会比一般离体的高。 相似文献
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Carlos B. Queirolo Carlos S. Andreo Hermann M. Niemeyer Luis J. Corcuera 《Phytochemistry》1983,22(11):2455-2458
-DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one), a hydroxamic acid from the Gramineae involved in the resistance of cereals to aphids, inhibits 相似文献
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A factor having the expected properties of the in vivo oxidant responsible for inactivating the in vivo light-activated chloroplast coupling factor 1 (CF1) has been partially purified from cell-free extracts of Dunaliella salina. This factor is highly polar, weakly acidic, and relatively temperature stable. The ability of this factor to inactivate light-activated CF1 is prevented if it is pretreated with reductants such as dithiothreitol. The factor has virtually no effect on the ethanol-induced, Mg2+ -dependent ATPase activity of the isolated CF1. 相似文献
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Preillumination of intact cells of the eukaryotic, halotolerant, cell-wall-less green alga Dunaliella salina induces a dark ATPase activity the magnitude of which is about 3–5-fold higher than the ATPase activity observed in dark-adapted cells. The light-induced activity arises from the activation and stabilization in vivo of chloroplast coupling factor 1 (CF1). This activity, 150–300 μmol ATP hydrolyzed/mg Chl per h, rapidly decays (with a half-time of about 6 min at room temperature) in intact cells but only slowly decays (with a half-time of about 45 min at room temperature) if the cells are lysed by osmotic shock immediately after illumination. The activated form of the ATPase in lysed cells is inhibited if the membranes are treated with ferri- but not ferrocyanide, suggesting that the stabilization of the activated form of CF1 is due to the reduction of the enzyme in vivo in the light. 相似文献