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Electron Transfer Proteins (electron + transfer_protein)
Selected AbstractsThe structure and dynamics in solution of Cu(I) pseudoazurin from Paracoccus pantotrophusPROTEIN SCIENCE, Issue 5 2000Gary S. Thompson Abstract The solution structure and backbone dynamics of Cu(I) pseudoazurin, a 123 amino acid electron transfer protein from Paracoccus pantotrophus, have been determined using NMR methods. The structure was calculated to high precision, with a backbone RMS deviation for secondary structure elements of 0.35 ± 0.06 A, using 1,498 distance and 55 torsion angle constraints. The protein has a double-wound Greek-key fold with two ,-helices toward its C-terminus, similar to that of its oxidized counterpart determined by X-ray crystallography. Comparison of the Cu(I) solution structure with the X-ray structure of the Cu(II) protein shows only small differences in the positions of some of the secondary structure elements. Order parameters S2, measured for amide nitrogens, indicate that the backbone of the protein is rigid on the picosecond to nanosecond timescale. [source] Functional association of cell death suppressor, Arabidopsis Bax inhibitor-1, with fatty acid 2-hydroxylation through cytochrome b5THE PLANT JOURNAL, Issue 1 2009Minoru Nagano Summary Bax inhibitor-1 (BI-1) is a widely conserved cytoprotective protein localized in the endoplasmic reticulum (ER) membrane. We identified Arabidopsis cytochrome b5 (AtCb5) as an interactor of Arabidopsis BI-1 (AtBI-1) by screening the Arabidopsis cDNA library with the split-ubiquitin yeast two-hybrid (suY2H) system. Cb5 is an electron transfer protein localized mainly in the ER membrane. In addition, a bimolecular fluorescence complementation (BiFC) assay and fluorescence resonance energy transfer (FRET) analysis confirmed that AtBI-1 interacted with AtCb5 in plants. On the other hand, we found that the AtBI-1-mediated suppression of cell death in yeast requires Saccharomyces cerevisiae fatty acid hydroxylase 1 (ScFAH1), which had a Cb5-like domain at the N terminus and interacted with AtBI-1. ScFAH1 is a sphingolipid fatty acid 2-hydroxylase localized in the ER membrane. In contrast, AtFAH1 and AtFAH2, which are functional ScFAH1 homologues in Arabidopsis, had no Cb5-like domain, and instead interacted with AtCb5 in plants. These results suggest that AtBI-1 interacts with AtFAHs via AtCb5 in plant cells. Furthermore, the overexpression of AtBI-1 increased the level of 2-hydroxy fatty acids in Arabidopsis, indicating that AtBI-1 is involved in fatty acid 2-hydroxylation. [source] Evaluation of SupermixTM as an in vitro model of human liver microsomal drug metabolismBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 5 2002Karthik Venkatakrishnan Abstract SUPERMIXTM is a commercially available formulation of insect cell-expressed human drug-metabolizing cytochrome P450 (CYP) isoforms, mixed in proportions that are optimized to parallel their relative activities in human liver microsomes. We have evaluated the apparent functional affinity and capacity of individual CYP isoforms in SUPERMIXTM in comparison with microsomes from a panel of 12 human livers, using enzyme kinetic studies of isoform-selective index reactions. In addition, we have measured the concentration of NADPH cytochrome P450 oxidoreductase (OR) in SUPERMIXTM and compared it with the concentrations of this accessory electron transfer protein in human liver microsomes. No important differences were evident in the catalytic activities of CYPs 1A2, 2C8, 2C9, 2C19, 2D6 and 3A4 between SUPERMIXTM and human liver microsomes. However, SUPERMIXTM lacks CYP2B6 activity and did not hydroxylate the antidepressant bupropion, a clinically relevant substrate of this enzyme. In addition, the concentration of OR in SUPERMIXTM (1198 pmol mg protein,1) is 17-fold higher than the mean value in human liver microsomes (70 pmol mg protein,1). In conclusion, SUPERMIXTM lacks CYP2B6 activity and contains supraphysiological concentrations of the accessory electron transfer protein OR. These factors should be considered when this formulation is used as an in vitro model in human liver microsomal drug metabolism studies. Copyright © 2002 John Wiley & Sons, Ltd. [source] Insights into the design of a hybrid system between Anabaena ferredoxin-NADP+ reductase and bovine adrenodoxinFEBS JOURNAL, Issue 4 2003Merche Faro The opportunity to design enzymatic systems is becoming more feasible due to detailed knowledge of the structure of many proteins. As a first step, investigations have aimed to redesign already existing systems, so that they can perform a function different from the one for which they were synthesized. We have investigated the interaction of electron transfer proteins from different systems in order to check the possibility of heterologous reconstitution among members of different chains. Here, it is shown that ferredoxin-NADP+ reductase from Anabaena and adrenodoxin from bovine adrenal glands are able to form optimal complexes for thermodynamically favoured electron transfer reactions. Thus, electron transfer from ferredoxin-NADP+ reductase to adrenodoxin seems to proceed through the formation of at least two different complexes, whereas electron transfer from adrenodoxin to ferredoxin-NADP+ reductase does not take place due because it is a thermodynamically nonfavoured process. Moreover, by using a truncated adrenodoxin form (with decreased reduction potential as compared with the wild-type) ferredoxin-NADP+ reductase is reduced. Finally, these reactions have also been studied using several ferredoxin-NADP+ reductase mutants at positions crucial for interaction with its physiological partner, ferredoxin. The effects observed in their reactions with adrenodoxin do not correlate with those reported for their reactions with ferredoxin. In summary, our data indicate that although electron transfer can be achieved in this hybrid system, the electron transfer processes observed are much slower than within the physiological partners, pointing to a low specificity in the interaction surfaces of the proteins in the hybrid complexes. [source] A novel NADPH-dependent oxidoreductase with a unique domain structure in the hyperthermophilic Archaeon, Thermococcus litoralisFEMS MICROBIOLOGY LETTERS, Issue 1 2008András Tóth Abstract Thermococcus litoralis, a hyperthermophilic Archaeon, is able to reduce elemental sulfur during fermentative growth. An unusual gene cluster (nsoABCD) was identified in this organism. In silico analysis suggested that three of the genes (nsoABC) probably originated from Eubacteria and one gene (nsoD) from Archaea. The putative NsoA and NsoB are similar to NuoE- and NuoF-type electron transfer proteins, respectively. NsoC has a unique domain structure and contains a GltD domain, characteristic of glutamate synthase small subunits, which seems to be integrated into a NuoG-type sequence. Flavin and NAD(P)H binding sites and conserved cysteines forming iron,sulfur clusters binding motifs were identified in the protein sequences deduced. The purified recombinant NsoC contains one FAD cofactor per protein molecule and catalyzes the reduction of polysulfide with NADPH as an electron donor and it also reduces oxygen. It was concluded that the Nso complex is a new type of NADPH-oxidizing enzyme using sulfur and/or oxygen as an electron acceptor. [source] Weak interactions and molecular recognition in systems involving electron transfer proteinsTHE CHEMICAL RECORD, Issue 4 2001Shun Hirota Abstract Electrostatic interactions and other weak interactions between amino acid side chains on protein surfaces play important roles in molecular recognition, and the mechanism of their intermolecular interactions has gained much interest. We established that charged peptides are useful for investigating the molecular recognition character of proteins and their molecular interaction induced structural changes. Positively charged lysine peptides competitively inhibited electron transfer from reduced cytochrome f (cyt f) or cytochrome c (cyt c) to oxidized plastocyanin (PC), due to neutralization of the negatively charged site of PC by formation of PC,lysine peptide complexes. Lysine peptides also inhibited electron transfer from cyt c to cytochrome c peroxidase. Likewise, negatively charged aspartic acid peptides interacted with the positively charged sites of cyt f and cyt c, and competitively inhibited electron transfer from reduced cyt f or cyt c to oxidized PC and from [Fe(CN)6]4, to oxidized cyt c. Changes in the geometry and a shift to a higher redox potential of the active site Cu of PC on oligolysine binding were detected by spectroscopic and electrochemical measurements, owing to the absence of absorption in the visible region for lysine peptides. Structural and redox potential changes were also observed for cyt f and cyt c by interaction with aspartic acid peptides. ©2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:290,299, 2001 [source] Isotropic 13C Hyperfine Coupling Constants Distinguish Neutral from Anionic Ubiquinone-Derived Radicals,CHEMPHYSCHEM, Issue 18 2009Scott E. Boesch A radical notion: Calculated isotropic 13C hyperfine coupling constants are distinctly different for the anionic ubisemiquinone model UQ., (picture, left) rather than the protonated UQH. (picture, right) and can distinguish between the two in electron transfer proteins such as cytochrome bo3, cytochrome bc1, or photosynthetic reaction centers. [source] | |||||||||||||