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991.
A genomewide screen for petite-negative yeast strains yields a new subunit of the i-AAA protease complex 下载免费PDF全文
Unlike many other organisms, the yeast Saccharomyces cerevisiae can tolerate the loss of mitochondrial DNA (mtDNA). Although a few proteins have been identified that are required for yeast cell viability without mtDNA, the mechanism of mtDNA-independent growth is not completely understood. To probe the relationship between the mitochondrial genome and cell viability, we conducted a microarray-based, genomewide screen for mitochondrial DNA-dependent yeast mutants. Among the several genes that we discovered is MGR1, which encodes a novel subunit of the i-AAA protease complex located in the mitochondrial inner membrane. mgr1Delta mutants retain some i-AAA protease activity, yet mitochondria lacking Mgr1p contain a misassembled i-AAA protease and are defective for turnover of mitochondrial inner membrane proteins. Our results highlight the importance of the i-AAA complex and proteolysis at the inner membrane in cells lacking mitochondrial DNA. 相似文献
992.
Day SM Westfall MV Fomicheva EV Hoyer K Yasuda S La Cross NC D'Alecy LG Ingwall JS Metzger JM 《Nature medicine》2006,12(2):181-189
The myofilament protein troponin I (TnI) has a key isoform-dependent role in the development of contractile failure during acidosis and ischemia. Here we show that cardiac performance in vitro and in vivo is enhanced when a single histidine residue present in the fetal cardiac TnI isoform is substituted into the adult cardiac TnI isoform at codon 164. The most marked effects are observed under the acute challenges of acidosis, hypoxia, ischemia and ischemia-reperfusion, in chronic heart failure in transgenic mice and in myocytes from failing human hearts. In the isolated heart, histidine-modified TnI improves systolic and diastolic function and mitigates reperfusion-associated ventricular arrhythmias. Cardiac performance is markedly enhanced in transgenic hearts during reperfusion despite a high-energy phosphate content similar to that in nontransgenic hearts, providing evidence for greater energetic economy. This pH-sensitive 'histidine button' engineered in TnI produces a titratable molecular switch that 'senses' changes in the intracellular milieu of the cardiac myocyte and responds by preferentially augmenting acute and long-term function under pathophysiological conditions. Myofilament-based inotropy may represent a therapeutic avenue to improve myocardial performance in the ischemic and failing heart. 相似文献
993.
Path integration and the neural basis of the 'cognitive map' 总被引:1,自引:0,他引:1
McNaughton BL Battaglia FP Jensen O Moser EI Moser MB 《Nature reviews. Neuroscience》2006,7(8):663-678
The hippocampal formation can encode relative spatial location, without reference to external cues, by the integration of linear and angular self-motion (path integration). Theoretical studies, in conjunction with recent empirical discoveries, suggest that the medial entorhinal cortex (MEC) might perform some of the essential underlying computations by means of a unique, periodic synaptic matrix that could be self-organized in early development through a simple, symmetry-breaking operation. The scale at which space is represented increases systematically along the dorsoventral axis in both the hippocampus and the MEC, apparently because of systematic variation in the gain of a movement-speed signal. Convergence of spatially periodic input at multiple scales, from so-called grid cells in the entorhinal cortex, might result in non-periodic spatial firing patterns (place fields) in the hippocampus. 相似文献
994.
Jensen ON 《Nature reviews. Molecular cell biology》2006,7(6):391-403
Post-translational modifications define the functional and structural plasticity of proteins in archaea, prokaryotes and eukaryotes. Multi-site protein modification modulates protein activity and macromolecular interactions and is involved in a range of fundamental molecular processes. Combining state-of-the-art technologies in molecular cell biology, protein mass spectrometry and bioinformatics, it is now feasible to discover and study the structural and functional roles of distinct protein post-translational modifications. 相似文献
995.
Bladder cancer is a common malignancy in the United States. Although urine cytology is a useful adjunct in both diagnosis and follow-up and is highly sensitive for detecting high-grade tumors, it is limited by decreased sensitivity in detecting low-grade tumors, which constitute the majority of new diagnoses. Additional screening tests with high sensitivity and specificity for urothelial tumors of all grades are indicated to help improve the diagnostic ability of urine cytology as well as to reduce the need for frequent cystoscopies, especially in those with low-risk disease. Several assays have been developed, with the ImmunoCyt/uCyt+ test (DiagnoCure, Inc., Québec, Canada) being especially promising. Recent studies on the applicability and efficacy of ImmunoCyt/uCyt+ testing are reviewed, as are its sensitivity, specificity, and predictive value in the follow-up and screening of urothelial malignancies. 相似文献
996.
Gene structure and chromosomal localization of mouse cyclin G2 (Ccng2) 总被引:18,自引:0,他引:18
Cyclins are essential activators of cyclin-dependent kinases (Cdk) which, in turn, play pivotal roles in controlling transition through cell-cycle checkpoints. Cyclin G2 is a recently discovered second member of the G-type cyclins. The two members of the G-type cyclins, cyclin G1 and cyclin G2, share high structural similarity but their function remains to be defined. Here we characterize the structure of the mouse cyclin G2 gene by first cloning and sequencing the full-length mouse cyclin G2 cDNA. The cyclin G2 cDNA was used to isolate the cyclin G2 gene from a BAC library and to establish that the gene was transcribed from eight exons spanning a total of 8604 bp. The cyclin G2 gene was mapped by fluorescence in situ hybridization (FISH) to mouse chromosome 5E3.3.–F1.3. This region is syntenic to a region on human chromosome 4. The expression of cyclins G1 and G2 was examined in various tissues, but no correlation between expression patterns of the two genes was observed. However, during hepatic ontogenesis the cyclin G2 expression level decreased with age, whereas cyclin G1 expression increased. Transient expression of cyclin G2-green fluorescent protein (GFP) fusion protein in NIH3T3 cells showed that cyclin G2 is essentially a cytoplasmic protein, in contrast to the largely nuclear localization of cyclin G1. Our data suggest that, despite the close structural similarity between mouse cyclins G1 and G2, these proteins most likely perform distinct functions. 相似文献
997.
998.
Letavic MA Bronk BS Bertsche CD Casavant JM Cheng H Daniel KL George DM Hayashi SF Kamicker BJ Kolosko NL Norcia LJ Oberton VD Rushing MA Santoro SL 《Bioorganic & medicinal chemistry letters》2002,12(19):2771-2774
The stereoselective synthesis of two novel series of tribasic macrocyclic antibiotics with potent in vitro activity against Pasteurella multocida and Escherichia coli strains of bacteria is described. The in vitro activity can be significantly influenced by the nature of the substituents on the C-4" aminoalcohol, with the stereochemistry of the C-4" alcohol playing a less critical role. The effect of substitution and stereochemistry on the in vivo activity in a murine model of respiratory infection is also described. 相似文献
999.
Strains of Serpulina hyodysenteriae and Serpulina innocens produced a cell-associated sucrase activity when grown in a medium containing sucrose. S. hyodysenteriae B204 sucrase activity cleaved sucrose and, to a lesser extent, raffinose and had a pH optimum of 5.7 to 6.2. This is the first report of an inducible enzyme produced by either S. hyodysenteriae or S. innocens. 相似文献
1000.
Seed production and outbreaks of non-cyclic rodent populations in deciduous forests 总被引:11,自引:1,他引:11
Thomas Secher Jensen 《Oecologia》1982,54(2):184-192
Summary In a 10-year study period, outbreaks of the bank vole, Clethrionomys glareolus, Schreber only occurred in years following huge seed production of European beech, Fagus sylvatica. Intensive winter reprodution preceded the outbreaks, in contrast to a normal breeding season from April through September. No winter reproduction occurred in nearby populations from habitats without mast production. During the winter, the average weight of C. glareolus remained high in the mast forests and the age structure resembled that of a summer breeding population. Despite excess energy requirements of winter breeding, survival rates were similar to that of non-breeding winter populations. In mast years, rodent consumption in the beech forest was estimated as 1.0–10.3% of endosperm production available to postdispersal seed predators. Between mast years rodent consumption made up 30–100% of endosperm production available. Mast years occurred at irregular intervals and seed production seems to be synchronized between individual trees over large areas and induced by climatic events. These phenomena lead to seed predator satiation. 相似文献