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201.
Francesca Zito Joelle Vinh Jean-Luc Popot Giovanni Finazzi 《The Journal of biological chemistry》2002,277(14):12446-12455
The cytochrome b(6)f complex of Chlamydomonas reinhardtii contains four large subunits and at least three small ones, PetG, PetL, and PetM, whose role and location are unknown. Chimeric proteins have been constructed, in which the C terminus of subunit IV is fused to either one or the other of the two putative N termini of PetL. Biochemical and functional analysis of the chimeras together with mass spectrometry analysis of the wild-type (WT) complex led to the following conclusions: (i) neither a free subunit IV C terminus nor a free PetL N terminus is required for assembly of the b(6)f complex; (ii) the first AUG codon in the sequence of the gene petL is used for initiation; (iii) the N terminus of WT PetL lies in the lumen; (iv) in the WT complex, the N terminus of PetL and the C terminus of subunit IV are within reach of each other; (v) the purified b(6)f complex from C. reinhardtii contains an eighth, hitherto unrecognized subunit, PetN; and (vi) the ability to perform state transitions is lost in the chimeric mutants, although (vii) the Q-cycle is unaffected. A structural hypothesis is presented to account for this peculiar phenotype. 相似文献
202.
Stéphane B Richard Jean-Luc Ferrer Marianne E Bowman Antonietta M Lillo Charles N Tetzlaff David E Cane Joseph P Noel 《The Journal of biological chemistry》2002,277(10):8667-8672
The enzyme 2-C-methyl-D-erythritol 2,4-cyclodiphosphate (MECDP) synthase catalyzes the conversion of 4-diphosphocytidyl-2-C-methyl-D-erythritol 2-phosphate (CDP-ME2P) to MECDP, a highly unusual cyclodiphosphate-containing intermediate on the mevalonate-independent pathway to isopentenyl diphosphate and dimethylallyl diphosphate. We now report two x-ray crystal structures of MECDP synthase refined to 2.8-A resolution. The first structure contains a bound Mn(2+) cation, and the second structure contains CMP, MECDP, and Mn(2+). The protein adopts a homotrimeric quaternary structure built around a central hydrophobic cavity and three externally facing active sites. Each of these active sites is located between two adjacent monomers. A tetrahedrally arranged transition metal binding site, potentially occupied by Mn(2+), sits at the base of the active site cleft. A phosphate oxygen of MECDP and the side chains of Asp(8), His(10), and His(42) occupy the metal ion coordination sphere. These structures reveal for the first time the structural determinants underlying substrate, product, and Mn(2+) recognition and the likely catalytic mechanism accompanying the biosynthesis of the cyclodiphosphate-containing isoprenoid precursor, MECDP. 相似文献
203.
204.
Rémy Ricoux Jean-Luc Boucher Dominique Mandon Yves-Michel Frapart Yann Henry Daniel Mansuy Jean-Pierre Mahy 《European journal of biochemistry》2003,270(1):47-55
Nitric oxide (NO) is a potent intra- and intercellular messenger involved in the control of vascular tone, neuronal signalling and host response to infection. In mammals, NO is synthesized by oxidation of l-arginine catalysed by hemeproteins called NO-synthases with intermediate formation of Nomega-hydroxy-l-arginine (NOHA). NOHA and some hydroxyguanidines have been shown to be able to deliver nitrogen oxides including NO in the presence of various oxidative systems. In this study, NOHA and a model compound, N-(4-chlorophenyl)-N'-hydroxyguanidine, were tested for their ability to generate NO in the presence of a haemprotein model, microperoxidase 8 (MP8), and hydrogen peroxide. Nitrite and nitrate production along with selective formation of 4-chlorophenylcyanamide was observed from incubations of N-(4-chlorophenyl)-N'-hydroxyguanidine in the presence of MP8 and hydrogen peroxide. In the case of NOHA, the corresponding cyanamide, Ndelta-cyano-L-ornithine, was too unstable under the conditions used and l-citrulline was the only product identified. A NO-specific conversion of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide to 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and formation of MP8-Fe-NO complexes were observed by EPR spectroscopy and low-temperature UV/visible spectroscopy, respectively. These results clearly demonstrate the formation of nitrogen oxides including NO from the oxidation of exogenous hydroxyguanidines by hydrogen peroxide in the presence of a minienzyme such as MP8. The importance of the bioactivation of endogenous (NOHA) or exogenous N-hydroxyguanidines by peroxidases of physiological interest remains to be established in vivo. 相似文献
205.
Gérard Tremblin Rozenn Cannuel Jean-Luc Mouget Malko Rech Jean-Michel Robert 《Journal of applied phycology》2000,12(6):557-566
Two prominent diatoms encountered in oyster-ponds,Haslea ostrearia and Skeletonema costatum,were grown in batch and in a semi-continuous modeunder light of different spectral quality, white, blueor blue-green. The last corresponded to white lightmodified by a water-soluble pigment, marennine,produced by H. ostrearia. After acclimation tothe different light treatments, the growth rates ofboth species showed little variation with respect tolight quality. The parameters for photosynthesisvs irradiance curves were very similar in H. ostrearia grown under the three light conditions,whereas S. costatum the maximum photosyntheticcapacity (on a chlorophyll a basis) wassignificantly reduced under blue-green light. Fluorescence analyses confirmed the data forphotosynthesis, with the operational fluorescenceyield decreasing faster with increasing irradiance inS. costatum grown under blue-green light. InH. ostrearia, fluorescence yields undersaturating irradiance were closely similar in thethree light conditions. The results are discussed inrelation with the prominent development of H.ostrearia that can outcompete other diatoms inoyster-ponds. 相似文献
206.
Campylobacter jejuni: Specific oligonucleotides and DNA probes for use in polymerase chain reaction-based diagnosis 总被引:7,自引:0,他引:7
Abstract A 1189 base-pair long DNA fragment, VS1, was isolated from a Campylobacter jejuni CIP 70.2 cosmid library and was found to contain regions specific for this bacterial species. For detection and identification of C. jejuni , two oligonucleotides derived from the VS1 sequence were used as primers in polymerase chain reaction test on genomic DNAs from 38 Campylobacter and from 10 non- Campylobacter strains. A specific, 358 base-pair long DNA fragment was amplified only when C. jejuni DNA was used as a target. The detection limit of the amplification reaction was as low as 1.86 fg DNA, which is the equivalent of one C. jejuni genome. 相似文献
207.
M L North I Duwig P Delva C Metzinger G Dine J Dupoirieux E Alessandri R Genneret 《Revue fran?aise de transfusion et immuno-hématologie》1984,27(1):21-33
Hemoglobin E has been discovered casually in the blood of two French donors: one coming from the Alsace region, the other one coming from the Champagne region. In the two cases, the hemoglobin E is in an heterozygote state and takes the place of 33 per cent of the total haemoglobin in the first and 24 per cent in the second. We investigated in their families and found that other members of these families had hemoglobin E. Each time, it was associated with a microcytosis and polycythaemia without anemy or iron deficiency. The red cells morphology shows many microspherocytes and target-cells. There is no relationship between these two families and the research of an asiatic antecedent proved negative. These two observations give a supplementary proof that the geographic repartition of the hemoglobin E is larger than what we read in the first publications and shows the interest to study the hemoglobin of unexplained polycythaemia with microcytes in the blood of blood donors. 相似文献
208.
209.
Alain L. Bardou Pierre M. Auger Jean-Luc Chasse Renaud Seigneuric 《Acta biotheoretica》1997,45(3-4):227-236
Limitations of antiarrhythmic drugs on cardiac sudden death prevention appeared since the early 80's. The "Cardiac Arrhythmia
Suppression Trial"(CAST) showed more recently that mortality was significantly higher inpatients treated with some particular
antiarrhythmic drugs than in non-treated patients. In this field, our group recently demonstrated that a bolus of a Class
1B antiarrhythmic drug was able to trigger a ventricular fibrillation due to transient blocks induction.
The aim of the present work was to systematically study, by use of the van Capelle and Durrer (VCD) model which allows to
simulate ventricular activation wave propagation, the link between arrhythmogenic effects and the ability of transient blocks
to possibly degenerate in severe arrhythmias. A fragment of the ventricular wall is represented by an array of 16384elements
electrically coupled. Effects of induction of one or several transient blocks, as the effects of their size and duration on
possible induction of reentries have been studied. Results obtained show that various combinations between these different
parameters may trigger reentries, ventricular tachycardia and/or more complex patterns assimilable to ventricular fibrillation.
These results clearly evidence the fact that possible induction of transient blocks may directly be related to risk factor
associated to arrhythmogenic effects of antiarrhythmic drugs.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
210.
Marc Lecouvey Céline Frochot Laurent Miclo Piotr Orlewski Michel Marraud Jean-Luc Gaillard Manh Thong Cung Régis Vanderesse 《International journal of peptide research and therapeutics》1997,4(4-6):359-364
Summary The conformation of a benzodiazepine-like decapeptide corresponding to the YLGYLEQLLR fragment of a casein has been examined
in a sodium dodecyl sulfate micellar medium using circular dichroism, two-dimensional1H NMR spectroscopy and restrained molecular dynamics simulation. The decapeptide adopts an amphipathic 310-helicoid structure in which the E6...R10 ionic bridge stabilizes the C-terminus. 相似文献