排序方式: 共有61条查询结果,搜索用时 15 毫秒
31.
32.
33.
Wu SP Bellei M Mansy SS Battistuzzi G Sola M Cowan JA 《Journal of inorganic biochemistry》2011,105(6):806-811
Schizosaccharomyces pombe (Sp) ferredoxin contains a C-terminal electron transfer protein ferredoxin domain (etpFd) that is homologous to adrenodoxin. The ferredoxin has been characterized by spectroelectrochemical methods, and Mössbauer, UV-Vis and circular dichroism spectroscopies. The Mössbauer spectrum is consistent with a standard diferric [2Fe-2S]2+ cluster. While showing sequence homology to vertebrate ferredoxins, the E°' and the reduction thermodynamics for etpFd (− 0.392 V) are similar to plant-type ferredoxins. Relatively stable Cys to Ser derivatives were made for each of the four bound Cys residues and variations in the visible spectrum in the 380-450 nm range were observed that are characteristic of oxygen ligated clusters, including members of the [2Fe-2S] cluster IscU/ISU scaffold proteins. Circular dichroism spectra were similar and consistent with no significant structural change accompanying these mutations. All derivatives were active in an NADPH-Fd reductase cytochrome c assay. The binding affinity of Fd to the reductase was similar, however, Vmax reflecting rate limiting electron transfer was found to decrease ~ 13-fold. The data are consistent with relatively minor perturbations of both the electronic properties of the cluster following substitution of the Fe-bond S atom with O, and the electronic coupling of the cluster to the protein. 相似文献
34.
Alexey V. VershubskiiIlya V. Kuvykin Vladimir I. PriklonskiiAlexander N. Tikhonov 《Bio Systems》2011,103(2):164-179
In this work, we summarize results of computer simulation of electron and proton transport processes coupled to ATP synthesis in chloroplasts performed within the frames of a mathematical model developed as a system of differential equations for concentrations of electron carriers and hydrogen ion inside and outside the granal and stromal thylakoids. The model takes into account topological peculiarities and lateral heterogeneity of the chloroplast lamellar system. This allowed us to analyze the influence of restricted diffusion of protons inside small compartments of a chloroplast (e.g., in the narrow inter-thylakoid gap) on electron transport processes. The model adequately describes two modes of pH-dependent feedback control of electron transport associated with: (i) the acidification of the thylakoid lumen, which causes the slowing down of plastoquinol oxidation and stimulates an increase in dissipation of excess energy in PS2, and (ii) the alkalization of stroma, inducing the activation of the BBC (Bassham-Benson-Calvin) cycle and intensified consumption of ATP and NADPH. The influence of ATP on electron transport is mediated by modulation of the thylakoid membrane conductivity to protons through the ATP synthase complexes. We also analyze the contribution of alternative electron transport pathways to the maintenance of optimal balance between the energy donating and energy consuming stages of the light-induced photosynthetic processes. 相似文献
35.
Frazão C Aragão D Coelho R Leal SS Gomes CM Teixeira M Carrondo MA 《FEBS letters》2008,582(5):763-767
Detailed structural models of di-cluster seven-iron ferredoxins constitute a valuable resource for folding and stability studies relating the metal cofactors' role in protein stability. The here reported, hemihedric twinned crystal structure at 2.0 A resolution from Acidianus ambivalens ferredoxin, shows an integral 103 residues, physiologically relevant native form composed by a N-terminal extension comprising a His/Asp Zn(2+) site and the ferredoxin (betaalphabeta)(2) core, which harbours intact clusters I and II, a [3Fe-4S](1+/0) and a [4Fe-4S](2+/1+) centres. This is in contrast with the previously available ferredoxin structure from Sulfolofus tokodai, which was obtained from an artificial oxidative conversion with two [3Fe-4S](1+/0) centres and poor definition around cluster II. 相似文献
36.
Repair of x-ray damage in aging WI-38 cells 总被引:2,自引:0,他引:2
Rate of strand rejoining and the ability to perform repair replication were determined in young ad old X-irradiated WI-38 cells. No differences in either process were apparent and we conclude that reduced efficiency in one or both of them is not responsible for in vitro aging of human cells. 相似文献
37.
Non-photochemical (dark) increases in chlorophyll a fluorescence yield associated with non-photochemical reduction of redox carriers (Fnpr) have been attributed to the reduction of plastoquinone (PQ) related to cyclic electron flow (CEF) around photosystem I. In vivo, this rise in fluorescence is associated with activity of the chloroplast plastoquinone reductase (plastid NAD(P)H:plastoquinone oxidoreductase) complex. In contrast, this signal measured in isolated thylakoids has been attributed to the activity of the protein gradient regulation-5 (PGR5)/PGR5-like (PGRL1)-associated CEF pathway. Here, we report a systematic experimentation on the origin of Fnpr in isolated thylakoids. Addition of NADPH and ferredoxin to isolated spinach thylakoids resulted in the reduction of the PQ pool, but neither its kinetics nor its inhibitor sensitivities matched those of Fnpr. Notably, Fnpr was more rapid than PQ reduction, and completely insensitive to inhibitors of the PSII QB site and oxygen evolving complex as well as inhibitors of the cytochrome b6f complex. We thus conclude that Fnpr in isolated thylakoids is not a result of redox equilibrium with bulk PQ. Redox titrations and fluorescence emission spectra imply that Fnpr is dependent on the reduction of a low potential redox component (Em about − 340 mV) within photosystem II (PSII), and is likely related to earlier observations of low potential variants of QA within a subpopulation of PSII that is directly reducible by ferredoxin. The implications of these results for our understanding of CEF and other photosynthetic processes are discussed. 相似文献
38.
39.
Ken Okada 《FEBS letters》2009,583(8):1251-5065
The HO1 and PcyA genes, encoding heme oxygenase-1 (HO1) and phycocyanobilin (PCB):ferredoxin (Fd) oxidoreductase (PcyA), respectively, are required for chromophore synthesis in photosynthetic light-harvesting complexes, photoreceptors, and circadian clocks. In the PCB biosynthetic pathway, heme first undergoes cleavage to form biliverdin. I confirmed that Fd1 induced the formation of a stable and functional HO1 complex by the gel mobility shift assay. Furthermore, analysis by a chemical cross-linking technique designed to detect protein-protein interactions revealed that HO1 and PcyA directly interact with Fd in a 1:2 ratio. Thus, Fd1, a one-electron carrier protein in photosynthesis, drives the phycobilin biosynthetic pathway.
Structured summary
MINT-7014657: Fd1 (uniprotkb:P0A3C9) and HO1 (uniprotkb:Q8DLW1) bind (MI:0407) by comigration in non-denaturing gel electrophoresis (MI:0404)MINT-7014666: HO1 (uniprotkb:Q8DLW1 and Fd1 (uniprotkb:P0A3C9) bind (MI:0407) by cross-linking studies (MI:0030)MINT-7014675: PcyA (uniprotkb:P59288) and Fd1 (uniprotkb:P0A3C9) bind (MI:0407) by cross-linking studies (MI:0030) 相似文献40.
Ken Okada 《FEBS letters》2009,583(2):313-319
The metabolic pathways in apicoplasts of human malaria parasites are promising drug targets. The apicomplexan parasites exhibit delayed cell death when their apicoplast is impaired, but the metabolic pathways within apicoplasts are poorly understood. A nuclear-encoded heme oxygenase (HO)-like protein with an apicoplast-targeted bipartite transit peptide was identified in the Plasmodiumfalciparum genome. Purified mature recombinant PfHO protein converted heme into bilirubin IXα as confirmed by high-performance liquid chromatography. In addition, PfHO required an iron chelator such as deferoxamine for complete activity. These observations lead to the conclusion that a novel enzymatic heme degradation system is present in human malaria parasites. 相似文献