共查询到20条相似文献,搜索用时 8 毫秒
1.
E A Kapp S Daya C G Whiteley 《Biochemical and biophysical research communications》1990,167(3):1383-1392
Fluorimetry and spectrophotometry have been used to study the binding of dimethyl, dipropyl, dibutyl and diphenylnitrosamine to nicotinic acetylcholine receptor isolated, and purified, from Torpedo fuscomaculata. Scatchard analysis indicates that all four ligands are true agonists of the receptor exhibiting positive cooperative binding with the existence of more than one class of binding site. The number of binding sites for the nitrosamines approximates 2. Diphenylnitrosamine binds to the receptor more tightly at low concentrations (Kd1 = 1.3 microM) than the aliphatic nitrosamine (Kd1 = 8-12 microM). Yet at high concentrations all nitrosamines behaved with similar Kd values (27-38 microM). 相似文献
2.
《The International journal of biochemistry》1994,26(9):1081-1093
- 1.1. Superoxide was generated during the auto-oxidation of the antituberculous drug, isonicotinic acid hydrazide (INH), but not with its meta-isomer, nicotinic acid hydrazide (NH). During Fe2+-stimulated oxidation of INH and NH, aromatic hydroxylation occurred which was inhibited by the chelating agent, phytic acid.
- 2.2. A mixture of myeloperoxidase (MPO) and a hydrazide induced formation of compound III (oxyperoxidase) and aromatic hydroxylation which was stimulated by phytic acid. INH was considerably more potent than NH.
- 3.3. Co-oxidation of a hydrazide and thyroxine (T4) in the MPO system resulted in the formation of a pink-coloured product (maximum absorbance at 504 nm) which was more stable with NH than with INH.
- 4.4. The hydrazides and Cl− acted synergistically on MPO haem modification when co-oxidised in the MPO-H2O2 system. INH was more destructive than NH.
- 5.5. The different oxidative pathways of the hydrazides are consistent with the fact that an acyl intermediate of INH, unlike that of NH, is resonance stabilized.
3.
Kasheverov IE Rozhkova AM Zhmak MN Utkin IuN Tsetlin VI 《Bioorganicheskaia khimiia》2002,28(2):101-108
Two photoactivatable analogues of alpha-conotoxin GI with the benzoylphenylalanine residue (Bpa) substituted for His10 or Tyr11 were synthesized using the method of solid-phase peptide synthesis. In addition, alpha-conotoxin MI was chemically modified by placing an azidobenzoyl or a benzoylbenzoyl photo label at N alpha of Gly1 or N epsilon of Lys10. All the photoactivatable analogues were purified by HPLC, their structures were confirmed by MALDI MS, and the label positions in their molecules were localized by MS of their trypsinolysis fragments. All the analogues interacted with the nicotinic acetylcholine receptor (AChR) from Torpedo californica as efficiently as the native alpha-conotoxins, with the differences in the inhibition constants being within one order of magnitude under the same conditions. [125I]Derivatives prepared from all the analogues retained the ability to be bound by AChR and were used in the photoinduced AChR cross-linking. All the AChR subunits were found to be cross-linked to the photoactivatable analogues, with the linking depending on both the chemical nature of label and its position in the alpha-conotoxin molecule. 相似文献
4.
Pagán OR Eterović VA Garcia M Vergne D Basilio CM Rodríguez AD Hann RM 《Biochemistry》2001,40(37):11121-11130
Long-chain alkanols are general anesthetics which can also act as uncharged noncompetitive inhibitors of the peripheral nicotinic acetylcholine receptor (AChR) by binding to one or more specific sites on the AChR. Cembranoids are naturally occurring, uncharged noncompetitive inhibitors of peripheral and neuronal AChRs, which have no demonstrable general anesthetic activity in vivo. In this study, [3H]tenocyclidine ([3H]TCP), an analogue of the cationic noncompetitive inhibitor phencyclidine (PCP), was used to characterize the cembranoid and long-chain alkanol sites on the desensitized Torpedo californica AChR and to investigate if these sites interact. These studies confirm that there is a single cembranoid site which sterically overlaps the [3H]TCP channel site. This cembranoid site probably also overlaps the sites for the cationic noncompetitive inhibitors, procaine and quinacrine. Evidence is also presented for one or more allosteric cembranoid sites which negatively modulate cembranoid affinity for the inhibitory site. In contrast, long-chain alkanols inhibit [3H]TCP binding through an allosteric mechanism involving two or more alkanol sites which display positive cooperativity toward each other. Double inhibitor studies show that the cembranoid inhibitory site and the alkanol sites are not independent of each other but interfere allosterically with each other's inhibition of [3H]TCP binding. The simplest models consistent with the observed data are presented and discussed. 相似文献
5.
R J Lukas 《The International journal of biochemistry》1986,18(7):609-615
Polyclonal antisera raised against solubilized and purified nicotinic acetylcholine receptor (nAcChoR) from Electrophorus electroplax and a polyclonal anti-alpha-bungarotoxin antiserum have been studied by the use of four different radioimmunoassay protocols. The results indicate unique sensitivities of different assay techniques in analysis of antibody-antigen interactions, and serve as a model for immunological study of other integral membrane proteins. 相似文献
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Vicente Bermúdez Silvia S. Antollini Gaspar A. Fernández Nievas Marta I. Avelda?o Francisco J. Barrantes 《Journal of lipid research》2010,51(9):2629-2641
The nicotinic acetylcholine receptor (AChR) is in intimate contact with the
lipids in its native membrane. Here we analyze the possibility that it is the
intrinsic properties of the AChR that determine its partition into a given lipid
domain. Torpedo AChR or a synthetic peptide corresponding to
the AChR γM4 segment (the one in closer contact with lipids) was
reconstituted into “raft”-containing model
membranes. The distribution of the AChR was assessed by Triton X-100 extraction
in combination with fluorescence studies, and lipid analyses were performed on
each sample. The influence of rapsyn, a peripheral protein involved in AChR
aggregation, was studied. Raft-like domain aggregation was also
studied using membranes containing the ganglioside GM1 followed by GM1
crosslinking. The γM4 peptide displays a marked preference for
raft-like domains. In contrast, AChR alone or in the
presence of rapsyn or ganglioside aggregation exhibits no such preference for
raft-like domains, but it does cause a significant reduction in the total amount
of these domains. The results indicate that the distribution of the AChR in
lipid domains cannot be due exclusively to the intrinsic physicochemical
properties of the protein and that there must be an external signal in native
cell membranes that directs the AChR to a specific membrane domain. 相似文献
8.
Antigenic sites of the nicotinic acetylcholine receptor cannot be predicted from the hydrophilicity profile 总被引:6,自引:0,他引:6
The amino acid sequences of the polypeptide chains of the acetylcholine receptor have recently been published. From the hydrophilicity profiles, it has been proposed that residues 161-166 of the alpha-chain might be an important antigenic site. We have synthesised a peptide containing this sequence and raised antisera to it. Here we report that this peptide does not represent an important antigenic site on the molecule, and that this region is probably inaccessible to antibodies. Based on the known DNA sequences and hydrophilicity profiles of the receptor chains, we suggest that many regions of high hydrophilicity may represent inter-domain regions of proteins. 相似文献
9.
Charton Y Guillonneau C Lockhart B Lestage P Goldstein S 《Bioorganic & medicinal chemistry letters》2008,18(6):2188-2193
Novel nicotinic ligands, characterized by the presence of an amino substituted cyclopropane ring connected to a pyridine nucleus, are described. Pharmacological investigation revealed that these compounds exhibit highest affinity for the rat alpha4beta2 subtype of the nicotinic receptor with no affinity for the muscarinic receptor. No appreciable affinity for the muscular or for the ganglionic nicotinic receptor was observed at concentrations up to 10 microM. The increase in cortical ACh release as well as a positive effect on memory in a social recognition test in rat are exemplified. 相似文献
10.
C D Barnes 《Life sciences》1966,5(20):1897-1902
11.
《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1995,670(1):162-166
A procedure is presented for the simultaneous identification and quantification of amphetamine (AP), methamphetamine (MA), methylenedioxyamphetamine (MDA) and methylenedioxymethamphetamine (MDMA) in human hair. The method involves decontamination of hair with dichloromethane and warm water, heat-alkaline hydrolysis in the presence of deuterated internal standards, liquid-liquid extraction and gas chromatography-mass spectrometry after derivatization with pentafluoropropionic anhydride-pentafluoropropanol. The limit of detection for AP, MA and MDA was 0.05 ng/mg using a 50-mg hair sample; for MDMA it was 0.1 ng/mg. Coefficients of variation ranged from 7 to 18%. This assay has been successfully utilized in the evaluation of the deposition of the drugs in hair obtained from various parts of the anatomy of a stimulant abuser. 相似文献
12.
Evolution of nicotinic acetylcholine receptor subunits 总被引:7,自引:0,他引:7
A phylogenetic tree of a gene family of nicotinic acetylcholine receptor
subunits was constructed using 84 nucleotide sequences of receptor subunits
from 18 different species in order to elucidate the evolutionary origin of
receptor subunits. The tree constructed showed that the common ancestor of
all subunits may have appeared first in the nervous system. Moreover, we
suggest that the alpha 1 subunits in the muscle system originated from the
common ancestor of alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, and beta 3
in the nervous system, whereas the beta 1, gamma, delta, and epsilon
subunits in the muscle system shared a common ancestor with the beta 2 and
beta 4 subunits in the nervous system. Using the ratio (f) of the number of
nonsynonymous substitutions to that of synonymous substitutions, we
predicted the functional importance of subunits. We found that the alpha 1
and alpha 7 subunits had the lowest f values in the muscle and nervous
systems, respectively, indicating that very strong functional constraints
work on these subunits. This is consistent with the fact that the alpha 1
subunit has sites binding to the ligand, and the alpha 7-containing
receptor regulates the release of the transmitter. Moreover, the window
analysis of the f values showed that strong functional constraints work on
the so-called M2 region in all five types of muscle subunits. Thus, the
window analysis of the f values is useful for evaluating the degree of
functional constraints in not only the entire gene region, but also the
within-gene subregion.
相似文献
13.
Molecular identification of nicotinic acid receptor 总被引:7,自引:0,他引:7
Soga T Kamohara M Takasaki J Matsumoto S Saito T Ohishi T Hiyama H Matsuo A Matsushime H Furuichi K 《Biochemical and biophysical research communications》2003,303(1):364-369
Nicotinic acid and its derivative, Acipimox, have been widely used in the treatment of hyperlipidemia. Pharmacological studies have demonstrated that they exert the beneficial effect through the activation of a Gi-protein-coupled receptor on adipocyte, which has remained elusive to date. Here we show that a novel GPCR, designated HM74b because of its high similarity to HM74, is a receptor for nicotinic acid. HM74b mRNA is found in human, murine, and rat adipose tissues. Nicotinic acid and Acipimox inhibit forskolin-stimulated intracellular cAMP accumulation in human HM74b-expressing cells and activate GTP gamma S binding in a dose-dependent manner. [3H]Nicotinic acid specifically binds to HM74b-expressing membrane and its binding is replaced by Acipimox. This finding will open a new phase of research on the physiological role of nicotinic acid and will be a clue to develop novel antihyperlipidemic drugs. 相似文献
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17.
The main immunogenic region of the nicotinic acetylcholine receptor: interaction of monoclonal antibodies with synthetic peptides 总被引:2,自引:0,他引:2
Monoclonal antibodies to the main immunogenic region of the nicotinic acetylcholine receptor have been studied with regard to their binding to synthetic peptides. It was found that monoclonal antibody 210 to the main immunogenic region binds to the synthetic fragment spanning residues 66 to 76 of the alpha subunits of the acetylcholine receptor from human muscle, but not to the homologous sequence from Xenopus. This parallels the reactivities of antibodies to the main immunogenic region with intact receptors from two species, and confirms the biological significance of the weak interactions observed between antibodies to this region and synthetic peptides. It also suggests that N alpha 68 and D alpha 71 are critical contact residues. 相似文献
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19.
Yuri N. Utkin Yasumaru Hatanaka Peter Franke Jan Machold Ferdinand Hucho Victor I. Tsetlin 《The protein journal》1995,14(4):197-203
Five singly modified nitrodiazirine derivatives of neurotoxin II (NT-II) fromNaja naja oxiana were obtained after NT-II reaction with N-hydroxysuccinimide ester of {2-nitro-4 [3-(trifluoromethyl)-3H-diazirin-3yl]phenoxy}acetic acid followed by Chromatographic separation of the products. To localize the label positions, each derivative was first UV-irradiated and then subjected to reduction, carboxymethylation, and trypsinolysis. Tryptic digests were separated by reversed phase-HPLC, the labeled peptides being identified by mass spectrometry. The derivatives containing the photolabel at the position Lys 25, Lys 26, Lys 44, or Lys 46 were [125I]iodinated by the chloramine T procedure. Each iodinated derivative was found to form photoinduced cross-links with the membrane bound nicotinic acetylcholine receptor (AChR) fromTorpedo californica. The pattern of labeling the receptor'sα, β, γ, orδ subunits was dependent on the photolabel position in the NT-II molecule and differed from that obtained earlier with an analogous series ofp-azidobenzoyl derivatives of NT-II. The results obtained indicate that (i) different sides of the neurotoxin molecule are involved in the AChR binding, and (ii) fragments of the different AChR subunits are located close together at the neurotoxin-binding sites. 相似文献
20.
We examined interactions between the endoplasmic reticulum (ER) chaperones calnexin (CN), ERp57, and immunological heavy chain-binding protein (BiP) and nicotinic acetylcholine receptor (nAChR) subunits. The three chaperones rapidly associate with newly synthesized nAChR subunits. Interactions between nAChR subunits and ERp57 occur via transient intermolecular disulfide bonds and do not require subunit N-linked glycosylation. The associations of ERp57 or CN with AChR subunits are long lived and prolong subunit lifetime approximately 10-fold. Coexpression of CN or ERp57 alone does not affect nAChR assembly or trafficking, but together they cause a significant decrease in nAChR expression and assembly. In contrast, associations with BiP are shorter lived and do not alter nAChR expression and assembly. However, a mutated BiP that slows its dissociation significantly increases its associations and decreases nAChR expression and assembly. Our results suggest that interactions with the chaperones regulate the levels of nAChRs assembled in the ER by stabilizing and sequestering subunits during assembly. 相似文献