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121.
Judith A. Heiny Violetta V. Kravtsova Frederic Mandel Tatiana L. Radzyukevich Boubacar Benziane Alexander V. Prokofiev Steen E. Pedersen Alexander V. Chibalin Igor I. Krivoi 《The Journal of biological chemistry》2010,285(37):28614-28626
The nicotinic acetylcholine receptor (nAChR) and the Na,K-ATPase functionally interact in skeletal muscle (Krivoi, I. I., Drabkina, T. M., Kravtsova, V. V., Vasiliev, A. N., Eaton, M. J., Skatchkov, S. N., and Mandel, F. (2006) Pflugers Arch. 452, 756–765; Krivoi, I., Vasiliev, A., Kravtsova, V., Dobretsov, M., and Mandel, F. (2003) Ann. N.Y. Acad. Sci. 986, 639–641). In this interaction, the specific binding of nanomolar concentrations of nicotinic agonists to the nAChR stimulates electrogenic transport by the Na,K-ATPase α2 isozyme, causing membrane hyperpolarization. This study examines the molecular nature and membrane localization of this interaction. Stimulation of Na,K-ATPase activity by the nAChR does not require ion flow through open nAChRs. It can be induced by nAChR desensitization alone, in the absence of nicotinic agonist, and saturates when the nAChR is fully desensitized. It is enhanced by noncompetitive blockers of the nAChR (proadifen, QX-222), which promote non-conducting or desensitized states; and retarded by tetracaine, which stabilizes the resting nAChR conformation. The interaction operates at the neuromuscular junction as well as on extrajunctional sarcolemma. The Na,K-ATPase α2 isozyme is enriched at the postsynaptic neuromuscular junction and co-localizes with nAChRs. The nAChR and Na,K-ATPase α subunits specifically coimmunoprecipitate with each other, phospholemman, and caveolin-3. In a purified membrane preparation from Torpedo californica enriched in nAChRs and the Na,K-ATPase, a ouabain-induced conformational change of the Na,K-ATPase enhances a conformational transition of the nAChR to a desensitized state. These results suggest a mechanism by which the nAChR in a desensitized state with high apparent affinity for agonist interacts with the Na,K-ATPase to stimulate active transport. The interaction utilizes a membrane-delimited complex involving protein-protein interactions, either directly or through additional protein partners. This interaction is expected to enhance neuromuscular transmission and muscle excitation. 相似文献
122.
Differences in protonation of ubiquinone and menaquinone in fumarate reductase from Escherichia coli
Maklashina E Hellwig P Rothery RA Kotlyar V Sher Y Weiner JH Cecchini G 《The Journal of biological chemistry》2006,281(36):26655-26664
Escherichia coli quinol-fumarate reductase operates with both natural quinones, ubiquinone (UQ) and menaquinone (MQ), at a single quinone binding site. We have utilized a combination of mutagenesis, kinetic, EPR, and Fourier transform infrared methods to study the role of two residues, Lys-B228 and Glu-C29, at the quinol-fumarate reductase quinone binding site in reactions with MQ and UQ. The data demonstrate that Lys-B228 provides a strong hydrogen bond to MQ and is essential for reactions with both quinone types. Substitution of Glu-C29 with Leu and Phe caused a dramatic decrease in enzymatic reactions with MQ in agreement with previous studies, however, the succinate-UQ reductase reaction remains unaffected. Elimination of a negative charge in Glu-C29 mutant enzymes resulted in significantly increased stabilization of both UQ-* and MQ-* semiquinones. The data presented here suggest similar hydrogen bonding of the C1 carbonyl of both MQ and UQ, whereas there is different hydrogen bonding for their C4 carbonyls. The differences are shown by a single point mutation of Glu-C29, which transforms the enzyme from one that is predominantly a menaquinol-fumarate reductase to one that is essentially only functional as a succinate-ubiquinone reductase. These findings represent an example of how enzymes that are designed to accommodate either UQ or MQ at a single Q binding site may nevertheless develop sufficient plasticity at the binding pocket to react differently with MQ and UQ. 相似文献
123.
Zielińska-Przyjemska Małgorzata Kaczmarek Mariusz Krajka-Kuźniak Violetta Wierzchowski Marcin Baer-Dubowska Wanda 《Molecular and cellular biochemistry》2020,474(1-2):113-123
Molecular and Cellular Biochemistry - The present study aimed to evaluate the cytotoxicity and its mechanism of five synthetic methoxy stilbenes, namely 3,4,4?-trimethoxy,... 相似文献
124.
La Cono V Smedile F Bortoluzzi G Arcadi E Maimone G Messina E Borghini M Oliveri E Mazzola S L'Haridon S Toffin L Genovese L Ferrer M Giuliano L Golyshin PN Yakimov MM 《Environmental microbiology》2011,13(8):2250-2268
In September 2008, an expedition of the RV Urania was devoted to exploration of the genomic richness of deep hypersaline anoxic lakes (DHALs) located in the Western part of the Mediterranean Ridge. Approximately 40 nautical miles SE from Urania Lake, the presence of anoxic hypersaline lake, which we named Thetis, was confirmed by swath bathymetry profiling and through immediate sampling casts. The brine surface of the Thetis Lake is located at a depth of 3258 m with a thickness of ≈ 157 m. Brine composition was found to be thalassohaline, saturated by NaCl with a total salinity of 348‰, which is one of highest value reported for DHALs. Similarly to other Mediterranean DHALs, seawater-brine interface of Thetis represents a steep pycno- and chemocline with gradients of salinity, electron donors and acceptors and posseses a remarkable stratification of prokaryotic communities, observed to be more metabolically active in the upper interface where redox gradient was sharper. [(14) C]-bicarbonate fixation analysis revealed that microbial communities are sustained by sulfur-oxidizing chemolithoautotrophic primary producers that thrive within upper interface. Besides microaerophilic autotrophy, heterotrophic sulfate reduction, methanogenesis and anaerobic methane oxidation are likely the predominant processes driving the ecosystem of Thetis Lake. 相似文献
125.
Capsule Great Bitterns bred successfully in ricefields in northern Italy, despite a marked delay to the breeding season compared to natural wetlands in the same geographical area. 相似文献
126.
An intertidal salt marsh fish assemblage inhabiting two creeks on North Bull Island, Dublin Bay was sampled monthly from June
2000 until May 2002. Water temperature and salinity were recorded in situ and samples were also taken for Suspended Particulate
Matter (SPM) and Chlorophyll a. All fish caught were weighed and measured and classified into functional guilds. A total of 6,549 individuals comprising
10 fish species from 10 families were recorded within the two creeks. The community was dominated by a few species, a feature
common to other estuarine fish populations. Of the 10 species found, the common goby, Pomatoschistus microps, the 3-spined stickleback, Gasterosteus aculeatus, the thick-lipped grey mullet, Chelon labrosus and the flounder, Platichthys flesus contributed 98.4% of all fish sampled. The fish population of the channels at Bull Island, Dublin, was dominated by the resident
gobies (true estuarine resident species), but also hosted juveniles of species such as the bass, Dicentrarchus labrax (marine juvenile migrant species). In turn, the nekton populations were dominated by the brown shrimp, Crangon crangon and the fairy shrimp, Palaemonetes varians especially in winter when fewer fish (numbers of species and abundance) were found. Multivariate analysis of fish diversity
and abundance revealed a strong seasonal pattern but there was little evidence of difference between creeks, nor of tidal
(spring/neap) effects. The estuarine fish using the intertidal marsh creeks have been little studied in Europe yet they play
a major role with the decapods in these habitats. This role needs to be quantified for a proper understanding of the system’s
function. 相似文献
127.
Constantinou-Kokotou Violetta 《International journal of peptide research and therapeutics》2002,9(2-3):143-152
Summary This article focuses on the synthesis and the biological activities of long chain amino alcohols. The methods for the synthesis
of these sphingosine analogues from various starting materials such as lipidic amino acids, serine, glyceraldehydes, long
chain 1,2-diols, are summarized in the first part of the review, followed by a discussion of the biological activities of
long chain amino alcohols and the applications for the synthesis of other bioactive compounds. 相似文献
128.
N. S. Yudin V. Vinogradov Sergey Tatyana A. Potapova Tatyana M. Naykova Violetta V. Sitnikova Igor V. Kulikov Viacheslav I. Khasnulin Cheche Konchuk Pavel E. Vloschinskii Sergey V. Ivanov Viktor F. Kobzev Aida G. Romaschenko Mikhail I. Voevoda 《Human genetics》1998,102(6):695-698
32-bp inactivating deletion in the β-chemokine receptor 5 (CCR5) gene, common in Nothern European populations, is associated
with reduced HIV-1 transmission risk and delayed disease progression. We have studied the deletion distribution in many populations
in Eurasia by polymerase chain reaction analysis of 531 DNA samples representing West and East Siberian, Central Asian, and
Far Eastern parts of Russia. An unusually high frequency (11.1%) of the deleted variant in natives of West Siberia, of Finno-Ugrian
descent, was observed. Furthermore, the deletion was infrequent in indigenous populations of Central Asia, East Siberia, the
Russian Far East, and Canada. We conclude that the Δccr5 distribution is limited primarily to Europeans and related western
Siberian Finno-Ugrian populations, with a sharp negative gradient toward the east along the territory of Russian Asia.
Received: 22 December 1997 / Accepted: 24 March 1998 相似文献
129.
58–62 kDa heat-shock proteins (hsp60) are molecular chaperonins involved in the process of protein folding, transmembrane translocation and assembly of oligomeric protein complexes. In eukaryotic cells hsp60 proteins have been found in mitochondria and chloroplasts. However, we have recently documented that, in addition to mitochondria, a hsp60-like protein is present in secretory granules of insulin-secreting beta cells. The pathway by which hsp60 is targeted to secretory granules was unknown. Here we report the existence of microvesicles involved in the transport of hsp60 protein. Immunoelectron microscopy of serial thin-sections of beta cells directly visualized stages associated with hsp60 delivery: attachment of microvesicles to a secretory granule, fusion with the secretory granule membrane and release of hsp60 molecules. Further biochemical and immunological analysis of microvesicles revealed the presence in their membrane of synaptophysin, a major component of synaptic-like microvesicles (SLMV) of neuroendocrine cells. Double immunogold labelling with antibodies to synaptophysin and hsp60 demonstrated co-localization of both proteins in the same microvesicles. Moreover, fusion of synaptophysin-positive microvesicles leaves synaptophysin incorporated, at least transiently, to secretory granule membranes. These findings suggest that, in beta cells, synaptic-like vesicles are involved in the transport and delivery of hsp60 and represent a novel pathway for protein transport and secretion. 相似文献
130.