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181.
Boekema EJ Hifney A Yakushevska AE Piotrowski M Keegstra W Berry S Michel KP Pistorius EK Kruip J 《Nature》2001,412(6848):745-748
Cyanobacteria are abundant throughout most of the world's water bodies and contribute significantly to global primary productivity through oxygenic photosynthesis. This reaction is catalysed by two membrane-bound protein complexes, photosystem I (PSI) and photosystem II (PSII), which both contain chlorophyll-binding subunits functioning as an internal antenna. In addition, phycobilisomes act as peripheral antenna systems, but no additional light-harvesting systems have been found under normal growth conditions. Iron deficiency, which is often the limiting factor for cyanobacterial growth in aquatic ecosystems, leads to the induction of additional proteins such as IsiA (ref. 3). Although IsiA has been implicated in chlorophyll storage, energy absorption and protection against excessive light, its precise molecular function and association to other proteins is unknown. Here we report the purification of a specific PSI-IsiA supercomplex, which is abundant under conditions of iron limitation. Electron microscopy shows that this supercomplex consists of trimeric PSI surrounded by a closed ring of 18 IsiA proteins binding around 180 chlorophyll molecules. We provide a structural characterization of an additional chlorophyll-containing, membrane-integral antenna in a cyanobacterial photosystem. 相似文献
182.
M L Michel A Samso C J Larsen 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(3):297-300
Murine cells continuously producing Friend viral complex were synchronized by Ficoll gradient centrifugation. Cells were isolated from different parts of the gradient and counts of budding particles were performed on ultra-thin sections. No significant differences were noticed, suggesting that viral release is not related to cell cycle. 相似文献
183.
184.
Summary Incorporation of linoleic acid14C by human erythrocyte membranes at different stades of blood conservation was studied for evaluating the metabolic state of these membranes. The incorporation was found to increase during the first two weeks of conservation for female and male blood, with important individual variation. However, this increase was more important for male blood. Then the incorporation decreased until the end of experimentation, after 6 weeks of conservation.
Chercheur du Centre de Transfusion Sanguine de Lyon, Service du DrA. Jouvenceaux. 相似文献
Chercheur du Centre de Transfusion Sanguine de Lyon, Service du DrA. Jouvenceaux. 相似文献
185.
Zollikofer CP Ponce de León MS Lieberman DE Guy F Pilbeam D Likius A Mackaye HT Vignaud P Brunet M 《Nature》2005,434(7034):755-759
Previous research in Chad at the Toros-Menalla 266 fossiliferous locality (about 7 million years old) uncovered a nearly complete cranium (TM 266-01-60-1), three mandibular fragments and several isolated teeth attributed to Sahelanthropus tchadensis. Of this material, the cranium is especially important for testing hypotheses about the systematics and behavioural characteristics of this species, but is partly distorted from fracturing, displacement and plastic deformation. Here we present a detailed virtual reconstruction of the TM 266 cranium that corrects these distortions. The reconstruction confirms that S. tchadensis is a hominid and is not more closely related to the African great apes. Analysis of the basicranium further indicates that S. tchadensis might have been an upright biped, suggesting that bipedalism was present in the earliest known hominids, and probably arose soon after the divergence of the chimpanzee and human lineages. 相似文献
186.
Allen JT Brown L Sanders R Moore CM Mustard A Fielding S Lucas M Rixen M Savidge G Henson S Mayor D 《Nature》2005,437(7059):728-732
Diatoms are unicellular or chain-forming phytoplankton that use silicon (Si) in cell wall construction. Their survival during periods of apparent nutrient exhaustion enhances carbon sequestration in frontal regions of the northern North Atlantic. These regions may therefore have a more important role in the 'biological pump' than they have previously been attributed, but how this is achieved is unknown. Diatom growth depends on silicate availability, in addition to nitrate and phosphate, but northern Atlantic waters are richer in nitrate than silicate. Following the spring stratification, diatoms are the first phytoplankton to bloom. Once silicate is exhausted, diatom blooms subside in a major export event. Here we show that, with nitrate still available for new production, the diatom bloom is prolonged where there is a periodic supply of new silicate: specifically, diatoms thrive by 'mining' deep-water silicate brought to the surface by an unstable ocean front. The mechanism we present here is not limited to silicate fertilization; similar mechanisms could support nitrate-, phosphate- or iron-limited frontal regions in oceans elsewhere. 相似文献
187.
The transcription factor Engrailed-2 guides retinal axons 总被引:1,自引:0,他引:1
Brunet I Weinl C Piper M Trembleau A Volovitch M Harris W Prochiantz A Holt C 《Nature》2005,438(7064):94-98
188.
Aubin I Adams CP Opsahl S Septier D Bishop CE Auge N Salvayre R Negre-Salvayre A Goldberg M Guénet JL Poirier C 《Nature genetics》2005,37(8):803-805
The mouse mutation fragilitas ossium (fro) leads to a syndrome of severe osteogenesis and dentinogenesis imperfecta with no detectable collagen defect. Positional cloning of the locus identified a deletion in the gene encoding neutral sphingomyelin phosphodiesterase 3 (Smpd3) that led to complete loss of enzymatic activity. Our knowledge of SMPD3 function is consistent with the pathology observed in mutant mice and provides new insight into human pathologies. 相似文献
189.
Moreira MC Klur S Watanabe M Németh AH Le Ber I Moniz JC Tranchant C Aubourg P Tazir M Schöls L Pandolfo M Schulz JB Pouget J Calvas P Shizuka-Ikeda M Shoji M Tanaka M Izatt L Shaw CE M'Zahem A Dunne E Bomont P Benhassine T Bouslam N Stevanin G Brice A Guimarães J Mendonça P Barbot C Coutinho P Sequeiros J Dürr A Warter JM Koenig M 《Nature genetics》2004,36(3):225-227
Ataxia-ocular apraxia 2 (AOA2) was recently identified as a new autosomal recessive ataxia. We have now identified causative mutations in 15 families, which allows us to clinically define this entity by onset between 10 and 22 years, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia and elevated alpha-fetoprotein (AFP). Ten of the fifteen mutations cause premature termination of a large DEAxQ-box helicase, the human ortholog of yeast Sen1p, involved in RNA maturation and termination. 相似文献
190.
Mutations in a member of the Ras superfamily of small GTP-binding proteins causes Bardet-Biedl syndrome 总被引:10,自引:0,他引:10
Fan Y Esmail MA Ansley SJ Blacque OE Boroevich K Ross AJ Moore SJ Badano JL May-Simera H Compton DS Green JS Lewis RA van Haelst MM Parfrey PS Baillie DL Beales PL Katsanis N Davidson WS Leroux MR 《Nature genetics》2004,36(9):989-993
RAB, ADP-ribosylation factors (ARFs) and ARF-like (ARL) proteins belong to the Ras superfamily of small GTP-binding proteins and are essential for various membrane-associated intracellular trafficking processes. None of the approximately 50 known members of this family are linked to human disease. Using a bioinformatic screen for ciliary genes in combination with mutational analyses, we identified ARL6 as the gene underlying Bardet-Biedl syndrome type 3, a multisystemic disorder characterized by obesity, blindness, polydactyly, renal abnormalities and cognitive impairment. We uncovered four different homozygous substitutions in ARL6 in four unrelated families affected with Bardet-Biedl syndrome, two of which disrupt a threonine residue important for GTP binding and function of several related small GTP-binding proteins. Analysis of the Caenorhabditis elegans ARL6 homolog indicates that it is specifically expressed in ciliated cells, and that, in addition to the postulated cytoplasmic functions of ARL proteins, it undergoes intraflagellar transport. These findings implicate a small GTP-binding protein in ciliary transport and the pathogenesis of a pleiotropic disorder. 相似文献