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881.
Ruggiero A Chambery A Di Maro A Pisante M Parente A Berisio R 《Protein and peptide letters》2007,14(1):97-100
PD-L4, a type 1 ribosome inactivating protein from Phytolacca dioica leaves, has been successfully crystallized using vapour diffusion methods and PEG 4000 as a precipitant agent. In addition, crystals of a PD-L4 mutant, which has been recently observed to have a lower polynucleotide-adenosine glycosidase activity on DNA, rRNA and poly (A) substrates, have been obtained. To gather information on PD-L4 reaction mechanism both forms have been co-crystallized with adenine, the major product of their catalytic reaction. Diffraction patterns extend to atomic resolution and crystals belong to the orthorhombic P2(1)2(1)2(1) space group, with one molecule in the asymmetric unit. Structure determination has been achieved using molecular replacement; preliminary electron density maps have clearly given evidence of adenine binding. 相似文献
882.
The phenomenon of blindsight has been largely studied and refers to residual abilities of blind patients without an acknowledged visual awareness. Similarly, "deaf hearing" might represent a further example of dissociation between detection and perception of sounds. Here we report the rare case of a patient with a persistent and complete cortical deafness caused by damage to the bilateral temporo-parietal lobes who occasionally showed unexpected reactions to environmental sounds despite she denied hearing. We applied for the first time electrophysiological techniques to better understand auditory processing and perceptual awareness of the patient. While auditory brainstem responses were within normal limits, no middle- and long-latency waveforms could be identified. However, event-related potentials showed conflicting results. While the Mismatch Negativity could not be evoked, robust P3-like waveforms were surprisingly found in the latency range of 600-700 ms. The generation of P3-like potentials, despite extensive destruction of the auditory cortex, might imply the integrity of independent circuits necessary to process auditory stimuli even in the absence of consciousness of sound. Our results support the reverse hierarchy theory that asserts that the higher levels of the hierarchy are immediately available for perception, while low-level information requires more specific conditions. The accurate characterization in terms of anatomy and neurophysiology of the auditory lesions might facilitate understanding of the neural substrates involved in deaf-hearing. 相似文献
883.
Transmembrane proteins allow cells to extensively communicate with the external world in a very accurate and specific way. They form principal nodes in several signaling pathways and attract large interest in therapeutic intervention, as the majority pharmaceutical compounds target membrane proteins. Thus, according to the current genome annotation methods, a detailed structural/functional characterization at the protein level of each of the elements codified in the genome is also required. The extreme difficulty in obtaining high-resolution three-dimensional structures, calls for computational approaches. Here we review to which extent the efforts made in the last few years, combining the structural characterization of membrane proteins with protein bioinformatics techniques, could help describing membrane proteins at a genome-wide scale. In particular we analyze the use of comparative modeling techniques as a way of overcoming the lack of high-resolution three-dimensional structures in the human membrane proteome. 相似文献
884.
Jiang P Cui M Zhao B Liu Z Snyder LA Benard LM Osman R Margolskee RF Max M 《The Journal of biological chemistry》2005,280(15):15238-15246
The detection of sweet-tasting compounds is mediated in large part by a heterodimeric receptor comprised of T1R2+T1R3. Lactisole, a broad-acting sweet antagonist, suppresses the sweet taste of sugars, protein sweeteners, and artificial sweeteners. Lactisole's inhibitory effect is specific to humans and other primates; lactisole does not affect responses to sweet compounds in rodents. By heterologously expressing interspecies combinations of T1R2+T1R3, we have determined that the target for lactisole's action is human T1R3. From studies with mouse/human chimeras of T1R3, we determined that the molecular basis for sensitivity to lactisole depends on only a few residues within the transmembrane region of human T1R3. Alanine substitution of residues in the transmembrane region of human T1R3 revealed 4 key residues required for sensitivity to lactisole. In our model of T1R3's seven transmembrane helices, lactisole is predicted to dock to a binding pocket within the transmembrane region that includes these 4 key residues. 相似文献
885.
Greening under High Light or Cold Temperature Affects the Level
of Xanthophyll-Cycle Pigments, Early Light-Inducible Proteins, and
Light-Harvesting Polypeptides in Wild-Type Barley and the
Chlorina f2 Mutant 总被引:1,自引:0,他引:1 下载免费PDF全文
Marianna Krl Alexander G. Ivanov Stefan Jansson Klaus Kloppstech Norman P.A. Huner 《Plant physiology》1999,120(1):193-204
Etiolated seedlings of wild type and the chlorina f2 mutant of barley (Hordeum vulgare) were exposed to greening at either 5°C or 20°C and continuous illumination varying from 50 to 800 μmol m−2 s−1. Exposure to either moderate temperature and high light or low temperature and moderate light inhibited chlorophyll a and b accumulation in the wild type and in the f2 mutant. Continuous illumination under these greening conditions resulted in transient accumulations of zeaxanthin, concomitant transient decreases in violaxanthin, and fluctuations in the epoxidation state of the xanthophyll pool. Photoinhibition-induced xanthophyll-cycle activity was detectable after only 3 h of greening at 20°C and 250 μmol m−2 s−1. Immunoblot analyses of the accumulation of the 14-kD early light-inducible protein but not the major (Lhcb2) or minor (Lhcb5) light-harvesting polypeptides demonstrated transient kinetics similar to those observed for zeaxanthin accumulation during greening at either 5°C or 20°C for both the wild type and the f2 mutant. Furthermore, greening of the f2 mutant at either 5°C or 20°C indicated that Lhcb2 is not essential for the regulation of the xanthophyll cycle in barley. These results are consistent with the thesis that early light-inducible proteins may bind zeaxanthin as well as other xanthophylls and dissipate excess light energy to protect the developing photosynthetic apparatus from excess excitation. We discuss the role of energy balance and photosystem II excitation pressure in the regulation of the xanthophyll cycle during chloroplast biogenesis in wild-type barley and the f2 mutant. 相似文献
886.
Ivanov AG Hendrickson L Krol M Selstam E Oquist G Hurry V Huner NP 《Plant & cell physiology》2006,47(8):1146-1157
Compared with wild type, the dgd1 mutant of Arabidopsis thaliana exhibited a lower amount of PSI-related Chl-protein complexes and lower abundance of the PSI-associated polypeptides, PsaA, PsaB, PsaC, PsaL and PsaH, with no changes in the levels of Lhca1-4. Functionally, the dgd1 mutant exhibited a significantly lower light-dependent, steady-state oxidation level of P700 (P700(+)) in vivo, a higher intersystem electron pool size, restricted linear electron transport and a higher rate of reduction of P700(+) in the dark, indicating an increased capacity for PSI cyclic electron transfer compared with the wild type. Concomitantly, the dgd1 mutant exhibited a higher sensitivity to and incomplete recovery of photoinhibition of PSI. Furthermore, dgd1 exhibited a lower capacity to undergo state transitions compared with the wild type, which was associated with a higher reduction state of the plastoquinone (PQ) pool. We conclude that digalactosyl-diacylglycerol (DGDG) deficiency results in PSI acceptor-side limitations that alter the flux of electrons through the photosynthetic electron chain and impair the regulation of distribution of excitation energy between the photosystems. These results are discussed in terms of thylakoid membrane domain reorganization in response to DGDG deficiency in A. thaliana. 相似文献
887.
Soil macrofauna and nitrogen on a sub-Antarctic island 总被引:4,自引:0,他引:4
Summary The densities, diets and habitat preferences of the soil macrofaunal species on sub-Antarctic Marion Island (47°S, 38°E) are described. Their role in N cycling on the island is assessed, using a mire-grassland community as an example. Primary production on the island is high and this leads to a substantial annual requirement of nutrients by the vegetation. This requirement must almost wholly be met by mineralization of nutrient reserves in the organic matter. Rates of peat nitrogen mineralization mediated by microorganisms alone are much too low to account for rates of N uptake by the vegetation. Although soil macroinvertebrates, and bacteria represent a very small fraction of the total N pool, their interaction accounts for most of the peat N mineralization, as indicated by the amounts of inorganic N released into solution in microcosms. Extrapolation of the microcosm results shows that the soil macrofauna (mainly earthworms) stimulate the release of enough N from the mire-grassland peat to account for maximum N mineralization rates calculated from temporal changes in peat inorganic N levels and plant uptake during the most active part of the growing season. Considering that large numbers of mesoand microinvertebrates occur and must also contribute to nutrient mineralization, the soil faunal component is clearly of crucial importance to nutrient cycling on Marion Island. This is probably true of all sub-Antarctic islands. 相似文献
888.
Paulina Paluchowska Marianna Tokarczyk Bozena Bogusz Iwona Skiba Alicja Budak 《Memórias do Instituto Oswaldo Cruz》2014,109(4):436-441
Over the last decades, Candida spp have been responsible for an
increasing number of infections, especially in patients requiring intensive care.
Knowledge of local epidemiology and analysis of the spread of these pathogens is
important in understanding and controlling their transmission. The aim of this study
was to evaluate the genetic diversity of 31 Candida albicans and
17 Candida glabrata isolates recovered from intensive care unit
patients from the tertiary hospital in Krakow between 2011-2012. The strains were
typed by random amplified polymorphic DNA (RAPD) polymerase chain reaction using five
primers (CD16AS, HP1247, ERIC-2, OPE-3 and OPE-18). The results of the present
investigation revealed a high degree of genetic diversity among the isolates. No
clonal relationship was found among the C. albicans strains, whereas
two C. glabrata isolates were identical. The source of
Candida infection appeared to be mostly endogenous; however, the presence
of two clonal C. glabrata strains suggested the possibility of
cross-transmission of these pathogens. Our study confirmed the high discriminatory
power of the RAPD technique in the molecular typing of Candida
clinical isolates. This method may be applied to the evaluation of transmission
routes of pathogenic fungi on a local level. 相似文献
889.
890.
Kele Péter Illyés Eszter Mezö Gábor Dóda Margit Mák Marianna Kaposi András D. Sebestyén Ferenc 《International journal of peptide research and therapeutics》1999,6(4):235-238
Summary Fluorescent derivatives of bovine neurotensin 8–13 fragment were prepared. For N-terminal labelling, 4-[7-hydroxycoumaryl]acetic
acid (Hca), 4-[7-methoxycoumaryl]acetic acid (Mca) and 2-amino-3-[4-[7-methoxycoumaryl]]propionic acid (Amp) were used while
the C-terminus of the peptide chain was elongated with Amp. The fluorescence excitation and emission spectra of the peptide
derivatives were studied. Hca- and Mca/Amp-derivatives were easily distinguishable because of the 60 nm shift of their emission
maxima. Compared with the natural sequence, the presence of an N-terminal label did not influence the biological potency in
a longitudinal muscle strip of guinea-pig ileum, while labelling at the C-terminus considerably reduced the activity of the
peptide. 相似文献