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181.
Till Pfennig Beate Herrmann Tim Bauer Edgar Schömig Dirk Gründemann 《生物化学与生物物理学报:生物膜》2013,1828(2):491-498
The liver is the principal source of glutamate in blood plasma. Recently we have discovered that efflux of glutamate from hepatocytes is catalyzed by the transporter OAT2 (human gene symbol SLC22A7). Organic anion transporter 2 (OAT2) is an integral membrane protein of the sinusoidal membrane domain; it is primarily expressed in liver and much less in kidney, both in rats and humans. Many years ago, Häussinger and coworkers have demonstrated in isolated perfused rat liver that benzoic acid or specific 2-oxo acid analogs of amino acids like e.g. 2-oxo-4-methyl-pentanoate (‘2-oxo-leucine’) strongly stimulate release of glutamate (up to 7-fold); ‘2-oxo-valine’ and the corresponding amino acids were without effect. The molecular mechanism of efflux stimulation has remained unclear. In the present study, OAT2 from human and rat were heterologously expressed in 293 cells. Addition of 1 mmol/l benzoic acid to the external medium increased OAT2-specific efflux of glutamate up to 20-fold; ‘2-oxo-leucine’ was also effective, but not ‘2-oxo-valine’. Similar effects were seen for efflux of radiolabeled orotic acid. Expression of OAT2 did not increase uptake of benzoic acid; thus, benzoic acid is no substrate, and trans-stimulation can be excluded. Instead, further experiments suggest that increased efflux of glutamate is caused by direct interaction of benzoic acid and specific 2-oxo acids with OAT2. We propose that stimulators bind to a distinct extracellular site and thereby accelerate relocation of the empty substrate binding site to the intracellular face. Increased glutamate efflux at OAT2 could be the main benefit of benzoate treatment in patients with urea cycle defects. 相似文献
182.
Adel Shalata Maria C. Ramirez Robert J. Desnick Nolan Priedigkeit Christoph Buettner Claudia Lindtner Mohammed Mahroum Muhammad Abdul-Ghani Feng Dong Nazik Arar Olga Camacho-Vanegas Rui Zhang Sandra C. Camacho Ying Chen Mwafaq Ibdah Ralph DeFronzo Virginia Gillespie Kevin Kelley Brian D. Dynlacht Sehyun Kim Marc J. Glucksman Zvi U. Borochowitz John A. Martignetti 《American journal of human genetics》2013
183.
Yingjie Li Shilpa Bali Sarah Borg Emanuel Katzmann Stuart J. Ferguson Dirk Schüler 《Journal of bacteriology》2013,195(18):4297-4309
The alphaproteobacterium Magnetospirillum gryphiswaldense synthesizes magnetosomes, which are membrane-enveloped crystals of magnetite. Here we show that nitrite reduction is involved in redox control during anaerobic biomineralization of the mixed-valence iron oxide magnetite. The cytochrome cd1-type nitrite reductase NirS shares conspicuous sequence similarity with NirN, which is also encoded within a larger nir cluster. Deletion of any one of these two nir genes resulted in impaired growth and smaller, fewer, and aberrantly shaped magnetite crystals during nitrate reduction. However, whereas nitrite reduction was completely abolished in the ΔnirS mutant, attenuated but significant nitrite reduction occurred in the ΔnirN mutant, indicating that only NirS is a nitrite reductase in M. gryphiswaldense. However, the ΔnirN mutant produced a different form of periplasmic d1 heme that was not noncovalently bound to NirS, indicating that NirN is required for full reductase activity by maintaining a proper form of d1 heme for holo-cytochrome cd1 assembly. In conclusion, we assign for the first time a physiological function to NirN and demonstrate that effective nitrite reduction is required for biomineralization of wild-type crystals, probably by contributing to oxidation of ferrous iron under oxygen-limited conditions. 相似文献
184.
European Wrynecks Jynx torquilla torquilla have generally been considered to be long‐distance Palaearctic–African migrants that spend the non‐breeding season in Sahelian Africa, where they have been reported regularly. Results from tracking individual birds showed that Wrynecks from two Central European populations migrated only relatively short distances to the Iberian Peninsula and northwestern Africa (c. 1500 km and 3000 km, respectively), compared with a minimum distance of about 4500 km to Sahelian Africa. Additionally, differences in wing lengths of populations from Central and Northern Europe support the idea of leap‐frog migration, populations from Northern Europe being long‐distance migrants with a non‐breeding distribution in Sahelian Africa. 相似文献
185.
Yimin Qian David Bolin Karin Conde-Knape Paul Gillespie Stuart Hayden Kuo-Sen Huang Andrée R. Olivier Tsutomu Sato Qing Xiang Weiya Yun Xiaolei Zhang 《Bioorganic & medicinal chemistry letters》2013,23(10):2936-2940
Glycogen synthase (GS) catalyzes the transfer of glucose residues from UDP-glucose to a glycogen polymer chain, a critical step for glucose storage. Patients with type 2 diabetes normally exhibit low glycogen levels and decreased muscle glucose uptake is the major defect in whole body glucose disposal. Therefore, activating GS may provide a potential approach for the treatment of type 2 diabetes. In order to identify non-carboxylic acids GS activators, we designed and synthesized a series of 2-N-alkyl- and 2-N-aryl-indazolone derivatives and studied their activity in activating human GS. 相似文献
186.
187.
The microbial communities inhabiting the mammalian intestinal tract play an important role in diverse aspects of host biology. However, little is known regarding the forces shaping variation in these communities and their influence on host fitness. To shed light on the contributions of host genetics, transmission and geography to diversity in microbial communities between individuals, we performed a survey of intestinal microbial communities in a panel of 121 house mice derived from eight locations across Western Europe using pyrosequencing of the bacterial 16S rRNA gene. The host factors studied included population structure estimated by microsatellite loci and mitochondrial DNA, genetic distance and geography. To determine whether host tissue (mucosa)‐associated communities display properties distinct from those of the lumen, both the caecal mucosa and contents were examined. We identified Bacteroides, Robinsoniella and Helicobacter as the most abundant genera in both the caecal content and mucosa‐associated communities of wild house mice. Overall, we found geography to be the most significant factor explaining patterns of diversity in the intestinal microbiota, with a comparatively weaker influence of host population structure and genetic distance. Furthermore, the influence of host genetic distance was limited to the mucosa communities, consistent with this environment being more intimately coupled to the host. 相似文献
188.
189.
An evidence-based consensus for the classification of arbuscular mycorrhizal fungi (Glomeromycota) 总被引:1,自引:0,他引:1
Dirk Redecker Arthur Schüßler Herbert Stockinger Sidney L. Stürmer Joseph B. Morton Christopher Walker 《Mycorrhiza》2013,23(7):515-531
The publication of a large number of taxon names at all levels within the arbuscular mycorrhizal fungi (Glomeromycota) has resulted in conflicting systematic schemes and generated considerable confusion among biologists working with these important plant symbionts. A group of biologists with more than a century of collective experience in the systematics of Glomeromycota examined all available molecular–phylogenetic evidence within the framework of phylogenetic hypotheses, incorporating morphological characters when they were congruent. This study is the outcome, wherein the classification of Glomeromycota is revised by rejecting some new names on the grounds that they are founded in error and by synonymizing others that, while validly published, are not evidence-based. The proposed “consensus” will provide a framework for additional original research aimed at clarifying the evolutionary history of this important group of symbiotic fungi. 相似文献
190.
Kim J. M. Mulders Yannick Weesepoel Packo P. Lamers Jean-Paul Vincken Dirk E. Martens René H. Wijffels 《Journal of applied phycology》2013,25(5):1421-1430
The effect of three different nutrient depletions (nitrogen, sulphur and magnesium) on the growth and pigment accumulation of the haptophyte Isochrysis aff. galbana (clone T-ISO) has been studied. Pigments were quantified based on RP-UHPLC-PDA-MSn analysis. All nutrient depletions led to reduced maximal biomass concentrations. Besides, all nutrient-depleted cultures accumulated 3-hydroxyechinenone. To our knowledge, this is the first time that 3-hydroxyechinenone has been found in I. aff. galbana T-ISO. Most 3-hydroxyechinenone, as well as the most echinenone and diatoxanthin, were found in the nitrogen-limited culture in which a more severe limitation resulted in higher cellular contents. Similar to accumulation of diatoxanthin, accumulation of 3-hydroxyechinenone and echinenone may be part of a global (stress) response mechanism to oversaturating light conditions. 相似文献