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61.
Marion Babot Paola Labarbuta Amanda Birch Sara Kee Matthew Fuszard Catherine H. Botting Ilka Wittig Heinrich Heide Alexander Galkin 《BBA》2014
An intriguing feature of mitochondrial complex I from several species is the so-called A/D transition, whereby the idle enzyme spontaneously converts from the active (A) form to the de-active (D) form. The A/D transition plays an important role in tissue response to the lack of oxygen and hypoxic deactivation of the enzyme is one of the key regulatory events that occur in mitochondria during ischaemia. We demonstrate for the first time that the A/D conformational change of complex I does not affect the macromolecular organisation of supercomplexes in vitro as revealed by two types of native electrophoresis. Cysteine 39 of the mitochondrially-encoded ND3 subunit is known to become exposed upon de-activation. Here we show that even if complex I is a constituent of the I + III2 + IV (S1) supercomplex, cysteine 39 is accessible for chemical modification in only the D-form. Using lysine-specific fluorescent labelling and a DIGE-like approach we further identified two new subunits involved in structural rearrangements during the A/D transition: ND1 (MT-ND1) and 39 kDa (NDUFA9). These results clearly show that structural rearrangements during de-activation of complex I include several subunits located at the junction between hydrophilic and hydrophobic domains, in the region of the quinone binding site. De-activation of mitochondrial complex I results in concerted structural rearrangement of membrane subunits which leads to the disruption of the sealed quinone chamber required for catalytic turnover. 相似文献
62.
Peganum harmala L. is a traditional Chinese and Uygur medicine used to treat cancer. Bioactivity‐guided fractionation was applied to determine the cytotoxic constituents from P. harmala. A novel triterpenoid and a phenolic glycoside were isolated and identified, as well as seven known compounds. The novel metabolites were elucidated to be 3α‐acetoxy‐27‐hydroxyolean‐12‐en‐28‐oic acid methyl ester ( 1 , OA) and N‐acetyl‐9‐syringinoside ( 9 ). Some compounds exhibited potent cytotoxicity against human tumor cells. Among them, OA showed the highest cytotoxicity against human lung cancer cells A549 with an IC50 value of 8.03 ± 0.81 μm . OA had a potent anti‐NSCLC cell activity by interfering with the epidermal growth factor receptor (EGFR) activation and its downstream signaling, and could exert an antiproliferative effect by inactivation of EGFR‐driven antiapoptotic pathway followed by the release of mitochondrial cytochrome c, which might prove to be a promising leading compound for the development of an anti‐lung cancer drug. 相似文献
63.
There is uncertainty in the literature regarding the number and location of fibronectin binding sites on denatured collagen. Although most attention has focused on a single site near the collagenase-sensitive region of each alpha chain, there is evidence for additional sites in other regions. We treated bovine type I collagen with cyanogen bromide, labeled the resulting mixture with fluorescein, and separated the peptides by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fluorescent bands were excised from the gel and dialyzed exhaustively to remove detergent. Titration of eight distinct fluorescent-labeled fragments with the 42-kDa gelatin-binding fragment of fibronectin caused increases in anisotropy that were fully reversible with unlabeled gelatin. By fitting the dose responses it was possible to calculate apparent K(d)'s whose values ranged between 1 and 4 microM. The largest fragment, alpha(2)-CB3,5, composing about 2/3 of the alpha(2) chain, when further digested with endoproteinase Lys-C, yielded at least three additional subfragments that also bound with similar affinities. Thus, there appear to be at least 14 distinct fibronectin binding sites of similar affinity in bovine type I collagen, five on each of the alpha(1) chains and four on the alpha(2) chain. Experiments with several synthetic peptides failed to reveal the exact nature of the binding site. 相似文献
64.
Steven Collins Njonte Wouamba Gervais Mouth Happi Michel Nguiam Pouofo Joseph Tchamgoue Jean‐Bosco Jouda Frida Longo Bruno Ndjakou Lenta Norbert Sewald Simeon Fogue Kouam 《化学与生物多样性》2020,17(9)
An extensive phytochemical study of the aerial parts of Vernonia guineensis Benth. (Asteraceae) led to the isolation of a new flavone, vernoguinoflavone and a naturally isolated glycerol ester, eicosanoic acid 2‐hydroxy‐1,3‐propanediyl ester, together with eighteen known secondary metabolites including quercetin, luteolin, vernopicrin, vernomelitensin, β‐amyrin, oleanolic acid, ursolic acid, lupeol, betulinic acid, β‐carotene, a mixture of stigmasterol and β‐sitosterol, β‐sitosterol‐3‐O‐β‐D‐glucoside, 2,3‐dihydroxypropyl heptacosanoate, pentacosanoic acid, docosan‐1‐ol, tritriacontan‐1‐ol, and heptatriacontan‐1‐ol. Eleven compounds are reported herein for the first time from this species. The structures of these compounds were elucidated on the basis of extensive spectroscopic analyses, particularly 1D and 2D NMR, and HR‐ESI‐MS and by comparison of their data with those reported in the literature. The crude extract, fractions and some isolated compounds were evaluated for their antibacterial activity against Gram‐negative bacteria: Escherichia coli (ATCC 25922), Shigella flexineri (NR 518), Salmonella muenchen, Salmonella typhimurium and Salmonella typhi (ATCC 19430). All the tested compounds demonstrated inhibitory activities against the tested enteric bacteria with MIC values ranging from 3.12 to 100 μg/ml. Three flavonoids isolated from the most active fraction demonstrated the best bioactivities against Escherichia coli, Salmonella muenchen and Salmonella typhimurium with MIC values ranging from 3.12 to 25 μg/mL. 相似文献
65.
Three new bases were isolated from Banisteriopsis caapi; they are harmine N-oxide, harmic acid methyl ester (methyl 7-methoxy-β-carboline 1-carboxylate) and harmalinic acid (7-methoxy-3,4-dihydro-β-carboline 1-carboxylic acid). 相似文献
66.
Increased nitric oxide (NO) production from hypoxic mammalian neurons increases cerebral blood flow (CBF) but also glutamatergic excitotoxicity and DNA fragmentation. Anoxia-tolerant freshwater turtles have evolved NO-independent mechanisms to increase CBF; however, the mechanism(s) of NO regulation are not understood. In turtle cortex, anoxia or NMDAR blockade depressed NO production by 27+/-3% and 41+/-5%, respectively. NMDAR antagonists also reduced the subsequent anoxic decrease in NO by 74+/-6%, suggesting the majority of the anoxic decrease is due to endogenous suppression of NMDAR activity. Prevention of NO-mediated damage during the transition to and from anoxia may be incidental to natural reductions of NMDAR activity in the anoxic turtle cortex. 相似文献
67.
68.
R. Chaaba N. Attia S. Hammami M. Smaoui K. Ben Hamda S. Mahjoub M. Hammami 《Molecular Biology》2008,42(6):829-833
We studied the relationship between apo E polymorphism and cholesteryl ester transfer protein (CETP) activity in 127 type
2 diabetic patients who did not take lipid lowering drugs. Furthermore, we studied the relationship between apo E and cholesteryl
ester transfer protein (CETP) in modulating plasma triglyceride and HDLcholesterol. Apo E genotypes were determined by PCR-RFLP,
and CETP activity was measured using an exogenous way. Our results showed that the CETP activity increased significantly in
the E2 carrier group compared to E4 carriers and E3/E3 homozygous (84.7 ± 43.9 vs. 62.5 ± 35.9 vs. 52.6 ± 23.6 nmol CE/ml/2h, respectively; p = 0.015). However, there was no association
between apo E polymorphism and lipid parameter variations. Even after adjustment for CETP activity, the results remained unchanged,
showing that CETP did not step in the relationship between apo E and lipid parameter variations. In conclusion there is an
association between apo E polymorphism and CETP activity, and this association did not affect the relationship between apo
E polymorphism and triglyceride and HDLcholesterol concentrations.
Published in Russian in Molekulyarnaya Biologiya, 2008, Vol. 42, No. 6, pp. 931–935.
The text was submitted by the authors in English. 相似文献
69.
70.
Two Italian CO2 springs allowed us to study the long-term effect of a 350–2600 μ mol mol–1 increase in CO2 concentrations on the surface structures of leaves of Quercus ilex L. Carbon dioxide increased the quantity of cuticular waxes, above an apparent threshold of 750 μ mol mol–1 CO2 . Leaf wettability was not modified by CO2 concentrations. Reduction in stomatal frequency was observable up to 750 μ mol mol–1 CO2 , the slope being almost the same as that estimated for the increase in CO2 concentration from pre-industrial times to the present. At higher concentrations, CO2 seemed to exert no more impact on stomatal frequency. 相似文献