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71.
High-frequency synaptic activity can cause facilitation of transmitter release due to accumulation of “residual Ca2+” at the nerve terminal. However, the mechanism of this phenomenon is still under debate. Here we show that, using extracellular recording from frog cutaneous pectoris muscle, paired-pulse facilitation (PPF) at the frog neuro-muscular junction decays in two or three-exponential manner depending upon the extracellular Ca2+ concentration ([Ca2+]e). First, second and “early” PPF components are analyzed and described in this study. Considering the dependence of PPF on [Ca2+]e, existence of several specific high-affinity intra-terminal Ca2+-binding sites that underlie the facilitation of transmitter release at the frog neuro-muscular junction is proposed. 相似文献
72.
This review summarizes data on the properties of L-lysine -oxidase, an enzyme that belongs to the group of oxidases of L-amino acids. This enzyme acts virtually only on L-lysine with a rather low K
m yielding -keto--aminocaproic acid. The decrease in the level of the essential amino acid L-lysine and the formation of hydrogen peroxide during the reaction possibly provide the basis for the unique properties of L-lysine -oxidase: cytotoxic, antitumor, antimetastatic, antiinvasive, antibacterial, and antiviral activities, as well as an immunomodulating effect. Native L-lysine -oxidase and its immobilized forms are promising tools for determination of concentration of L-lysine in various biological materials. 相似文献
73.
Abstract Marine vegetation of Port-Cros Island (National park). XII: on Acrochaetium molinieri sp. nov. and Lophosiphonia cristata Falkenberg. – Acrochaetium molinieri sp. nov. is characterized by its bicellular base; only one of these cells originates an erect filament. Lophosiphonia cristata, rarely mentioned from the Mediterranean, is richly illustrated and described in detail 相似文献
74.
《Bioscience, biotechnology, and biochemistry》2013,77(7):1644-1649
The relationships between the structural and energetic domains of lentil seedling amine oxidase (LSAO) were investigated using modifiers that target the active site and the carbohydrate moiety of the enzyme. An irreversible inhibitor, aminoguanidine, specifically modified the active site of the lentil enzyme, whereas sodium metaperiodate cleaves carbohydrate moieties covalently bound to the native enzyme. Differential scanning calorimetry (DSC) measurements were made on the modified LSAOs. Deconvolution of the reversible thermal DSC profiles of the modified enzyme gave three subpeaks (energetic domains), each of which was assigned to one of the three structural domains of the native protein. Our results led us to conclude that deglycosylation of LSAO has no effect on thermal stability, whereas binding of the inhibitor imparts more stability to the enzyme. 相似文献
75.
Stephanie Fanucchi 《FEBS letters》2009,583(22):3557-3562
A novel survival role of focal adhesion kinase (FAK) that involves its nuclear translocation and direct association with p53 has been demonstrated. Here we examined the relationship between the p53/FAK interaction and Ser46 phosphorylation of p53 (p-p53Ser46) in the apoptotic regulation of human esophageal squamous cell carcinoma (HOSCC) cell lines, expressing either wild type (wt) p53 or mutant (mt) p53-R175H. In contrast to the wt p53 cell lines, the mt p53-R175H cell line was resistant to staurosporine (STS)-mediated detachment and caspase-3 activation. Furthermore, despite the resistance of mt p53-R175H to Ser46 phosphorylation, both wt and mt HOSCC cells translocate FAK into the nucleus and maintain the p53/FAK interaction post STS treatment. These findings provide unique insight into how tumor cells harboring the R175H mutant may resist chemotherapeutic intervention.
Structured summary
MINT-7294020: FAK (uniprotkb:Q05397) physically interacts (MI:0915) with p53 (uniprotkb:P04637) by anti-bait coimmunoprecipitation (MI:0006) 相似文献76.
To counter antibiotic-resistant bacteria, we screened the Kitasato Institute for Life Sciences Chemical Library with bacterial quinol oxidase, which does not exist in the mitochondrial respiratory chain. We identified five prenylphenols, LL-Z1272β, γ, δ, ? and ζ, as new inhibitors for the Escherichia coli cytochrome bd. We found that these compounds also inhibited the E. coli bo-type ubiquinol oxidase and trypanosome alternative oxidase, although these three oxidases are structurally unrelated. LL-Z1272β and ? (dechlorinated derivatives) were more active against cytochrome bd while LL-Z1272γ, δ, and ζ (chlorinated derivatives) were potent inhibitors of cytochrome bo and trypanosome alternative oxidase. Thus prenylphenols are useful for the selective inhibition of quinol oxidases and for understanding the molecular mechanisms of respiratory quinol oxidases as a probe for the quinol oxidation site. Since quinol oxidases are absent from mammalian mitochondria, LL-Z1272β and δ, which are less toxic to human cells, could be used as lead compounds for development of novel chemotherapeutic agents against pathogenic bacteria and African trypanosomiasis. 相似文献
77.
During 30-months of storage at 4°C, potato (Solanum tuberosum L.) tubers progressively lose the ability to produce superoxide in response to wounding, resist microbial infection, and
develop a suberized wound periderm. Using differentially aged tubers, we demonstrate that Strboh A is responsible for the wound-induced oxidative burst in potato and aging attenuates its expression. In vivo superoxide production
and NADPH oxidase (NOX) activity from 1-month-old tubers increased to a maximum 18–24 h after wounding and then decreased
to barely detectable levels by 72 h. Wounding also induced a 68% increase in microsomal protein within 18 h. These wound-induced
responses were lost over a 25- to 30-month storage period. Superoxide production and NOX activity were inhibited by diphenylene
iodonium chloride, a specific inhibitor of NOX, which in turn effectively inhibited wound-healing and increased susceptibility
to microbial infection and decay in 1-month-old tubers. Wound-induced superoxide production was also inhibited by EGTA-mediated
destabilization of membranes. The ability to restore superoxide production to EGTA-treated tissue with Ca+2 declined with advancing tuber age, likely a consequence of age-related changes in membrane architecture. Of the five homologues
of NOX (Strboh A-D and F), wounding induced the expression of Strboh A in 6-month-old tubers but this response was absent in tubers stored for 25–30 months. Strboh
A thus mediates the initial burst of superoxide in response to wounding of potato tubers; loss of its expression increases
the susceptibility to microbial infection and contributes to the age-induced loss of wound-healing ability. 相似文献
78.
Spatial separation of litter decomposition and mycorrhizal nitrogen uptake in a boreal forest 总被引:4,自引:0,他引:4
Lindahl BD Ihrmark K Boberg J Trumbore SE Högberg P Stenlid J Finlay RD 《The New phytologist》2007,173(3):611-620
Our understanding of how saprotrophic and mycorrhizal fungi interact to re-circulate carbon and nutrients from plant litter and soil organic matter is limited by poor understanding of their spatiotemporal dynamics. In order to investigate how different functional groups of fungi contribute to carbon and nitrogen cycling at different stages of decomposition, we studied changes in fungal community composition along vertical profiles through a Pinus sylvestris forest soil. We combined molecular identification methods with 14C dating of the organic matter, analyses of carbon:nitrogen (C:N) ratios and 15N natural abundance measurements. Saprotrophic fungi were primarily confined to relatively recently (< 4 yr) shed litter components on the surface of the forest floor, where organic carbon was mineralized while nitrogen was retained. Mycorrhizal fungi dominated in the underlying, more decomposed litter and humus, where they apparently mobilized N and made it available to their host plants. Our observations show that the degrading and nutrient-mobilizing components of the fungal community are spatially separated. This has important implications for biogeochemical studies of boreal forest ecosystems. 相似文献
79.
Irina Vaseva Dessislava Todorova Jiří Malbeck Alena Trávníčková Ivana Macháčková 《Acta Physiologiae Plantarum》2008,30(2):151-155
Changes in cytokinin pool and cytokinin oxidase/dehydrogenase activity (CKX EC: 1.5.99.12) in response to increasing abscisic
acid (ABA) concentrations (0.5–10 μM) were assessed in the last fully expanded leaves and secondary roots of two pea (Pisum sativum) varieties with different vegetation periods. Certain organ diversity in CKX response to exogenous ABA was observed. Treatment
provoked altered cytokinin pool in the aboveground parts of both studied cultivars. Specific CKX activity was influenced significantly
basically in roots of the treated plants. Results suggest that ABA-mediated cytokinin pool changes are leaf-specific and involve
certain root signals in which CKX activity presents an important link. This enzymatic activity most probably regulates vascular
transport of active cytokinins from roots to shoots. 相似文献
80.
Mathew P. Daniels 《Molecular neurobiology》1997,14(3):143-170
Reciprocal signals between the motor axon and myofiber induce structural and functional differentiation in the developing
neuromuscular junction (NMJ). Elevation of presynaptic acetylcholine (ACh) release on nerve-muscle contact and the correlated
increase in axonal-free calcium are triggered by unidentified membrane molecules. Restriction of axon growth to the developing
NMJ and formation of active zones for ACh release in the presynaptic terminal may be induced by molecules in the synaptic
basal lamina, such as S-laminin, heparin binding growth factors, and agrin. Acetylcholine receptor (AChR) synthesis by muscle
cells may be increased by calcitonin gene-related peptide (CGRP), ascorbic acid, and AChR-inducing activity (ARIA)/heregulin,
which is the best-established regulator. Heparin binding growth factors, proteases, adhesion molecules, and agrin all may
be involved in the induction of AChR redistribution to form postsynaptic-like aggregates. However, the strongest case has
been made for agrin's involvement. “Knockout” experiments have implicated agrin as a primary anterograde signal for postsynaptic
differentiation and muscle-specific kinase (MuSK), as a putative agrin receptor. It is likely that both presynaptic and postsynaptic
differentiation are induced by multiple molecular signals. Future research should reveal the physiological roles of different
molecules, their interactions, and the identity of other molecular participants. 相似文献