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1.
Bixel MG Weise C Bolognesi ML Rosini M Brierly MJ Mellor IR Usherwood PN Melchiorre C Hucho F 《The Journal of biological chemistry》2001,276(9):6151-6160
To map the structure of a ligand-gated ion channel, we used the photolabile polyamine-containing toxin MR44 as photoaffinity label. MR44 binds with high affinity to the nicotinic acetylcholine receptor in its closed channel conformation. The binding stoichiometry was two molecules of MR44 per receptor monomer. Upon UV irradiation of the receptor-ligand complex, (125)I-MR44 was incorporated into the receptor alpha-subunit. From proteolytic mapping studies, we conclude that the site of (125)I-MR44 cross-linking is contained in the sequence alpha His-186 to alpha Leu-199, which is part of the extracellular domain of the receptor. This sequence partially overlaps in its C-terminal region with one of the three loops that form the agonist-binding site. The agonist carbachol and the competitive antagonist alpha-bungarotoxin had only minor influence on the photocross-linking of (125)I-MR44. The site where the hydrophobic head group of (125)I-MR44 binds must therefore be located outside the zone that is sterically influenced by agonist bound at the nicotinic acetylcholine receptor. In binding and photocross-linking experiments, the luminal noncompetitive inhibitors ethidium and triphenylmethylphosphonium were found to compete with (125)I-MR44. We conclude that the polyamine moiety of (125)I-MR44 interacts with the high affinity noncompetitive inhibitor site deep in the channel of the nicotinic acetylcholine receptor, while the aromatic ring of this compound binds in the upper part of the ion channel (i.e. in the vestibule) to a hydrophobic region on the alpha-subunit that is located in close proximity to the agonist binding site. The region of the alpha-subunit labeled by (125)I-MR44 should therefore be accessible from the luminal side of the vestibule. 相似文献
2.
Tumiatti V Minarini A Milelli A Rosini M Buccioni M Marucci G Ghelardini C Bellucci C Melchiorre C 《Bioorganic & medicinal chemistry》2007,15(6):2312-2321
The aim of the present paper was to investigate the role of the octamethylene spacer of methoctramine (1) on the biological profile. Thus, this spacer was incorporated into a dianiline or dipiperidine moiety to determine whether flexibility and the basicity of the inner nitrogen atoms are important determinants of potency with respect to muscarinic receptors. The most potent compound was 4, which displayed, in the functional assays, a comparable potency at muscarinic M(2) receptors with respect to 1, and, in the binding assays, a loss of potency and selectivity toward muscarinic M(1) and M(3) receptor subtypes. Both compounds were endowed with antinociceptive activity. Furthermore, in microdialysis tests in rat parietal cortex, they enhanced acetylcholine release, most likely by antagonizing presynaptic muscarinic receptor subtypes. 相似文献
3.
Bolognesi ML Bartolini M Tarozzi A Morroni F Lizzi F Milelli A Minarini A Rosini M Hrelia P Andrisano V Melchiorre C 《Bioorganic & medicinal chemistry letters》2011,21(9):2655-2658
Memoquin (1) is a lead compound multitargeted against Alzheimer’s disease (AD). It is an AChE inhibitor, free-radical scavenger, and inhibitor of amyloid-β (Aβ) aggregation. A new series of 1 derivatives was designed and synthesized by linking its 2,5-diamino-benzoquinone core with motifs that are present in the structure of known amyloid binding agents like curcumin, the benzofuran derivative SKF64346, or the benzothiazole bearing compounds KHG21834 and BTA-1. The weaker AChE inhibitory potencies and the concomitant nearly equipotent anti-amyloid activities of the new compounds with respect to 1 resulted in a more balanced biological profile against both targets. Selected compounds turned out to be effective Aβ aggregation inhibitors in a cell-based assay. By properly combining two or more distinct pharmacological properties in a molecule, we can achieve greater effectiveness compared to single-targeted drugs for investigating AD. 相似文献
4.
This study, conducted on isolated guinea pig ileum, was designed to establish the mechanism of presynaptic alpha 2-adrenoreceptor blockade by the tetramine disulfides, benextramine and pyrextramine. At 1 microM these drugs irreversibly blocked norepinephrine (NE)-induced inhibition of the twitch response to electrical stimulation. This may be the result of covalent bond formation between the disulfide bridge of the inhibitor and a thiol function at the receptor level through an interchange reaction since the benextramine carbon analogue did not affect NE response under the same conditions. Furthermore, NE (10 microM) failed to protect presynaptic alpha 2-adrenoreceptors from pyrextramine blockade whereas idazoxan (O.T microM) completely abolished the irreversible antagonism of pyrextramine (1 microM). This finding suggests that the tetramine disulfide binding site may coincide with that of idazoxan and is different from the NE binding site. 相似文献
5.
Martini E Norcini M Ghelardini C Manetti D Dei S Guandalini L Melchiorre M Pagella S Scapecchi S Teodori E Romanelli MN 《Bioorganic & medicinal chemistry》2008,16(23):10034-10042
A series of amides, structurally related to DM232 (unifiram) and DM235 (sunifiram), characterized by a 1,2,3,4-tetrahydropyrazino[2,1-a]isoindol-6(2H)-one, 1,4-diamino-cyclohexane or 1,4-diaminobenzene ring, have been synthesized and tested for cognition-enhancing activity in the mouse passive-avoidance test. Some of the compounds display good antiamnesic and procognitive activity, with higher potency than piracetam, while some cyclohexane derivatives are endowed with amnesia inducing properties. 相似文献
6.
Minarini A Marucci G Bellucci C Giorgi G Tumiatti V Bolognesi ML Matera R Rosini M Melchiorre C 《Bioorganic & medicinal chemistry》2008,16(15):7311-7320
Pirenzepine (2) is one of the most selective muscarinic M(1) versus M(2) receptor antagonists known. A series of 2 analogs, in which the piperazyl moiety was replaced by a cis- and trans-cyclohexane-1,2-diamine (3-6) or a trans- and cis-perhydroquinoxaline rings (7 and 8) were prepared, with the aim to investigate the role of the piperazine ring of 2 in the interaction with the muscarinic receptors. The structural change leading to compounds 3-6 abolished in binding assays the muscarinic M(1)/M(2) selectivity of 2, due to an increased M(2) affinity. Rather, compounds 3-6 displayed a reversed selectivity showing more affinity at the muscarinic M(2) receptor than at all the other subtypes tested. 相似文献
7.
Mariana Melchiorre Gastn E. Quero Rodrigo Parola Roberto Racca Victorio S. Trippi Ramiro Lascano 《Plant science》2009,177(6):618-628
The genus Lotus comprises a heterogeneous group of annual and perennial species. Lotus japonicus (with MG20 and Gifu ecotypes) has been adopted as one of the model legumes in genetic and genomic studies. Other Lotus species, such us Lotus burttii and Lotus filicaulis, have also been used in genetic and genomic studies because of their capacity to produce fertile progenies in crosses with L. japonicus. In the present work, physiological responses to salt stress in four Lotus genotypes were evaluated on the basis of growth and associated parameters, such as photosynthesis, ions, relative water content, oxidative damage and antioxidant system responses, using two NaCl levels applied by acclimation for up to 28 and 60 d. Growth responses varied with plant developmental stage in the four Lotus genotypes. L. japonicus MG20 was found to be a salt-tolerant genotype, mainly when exposed to salt stress at the young plant stage. The capacity of Lj MG20 to sustain growth under salt stress was correlated with enhancement of Superoxide dismutase and Glutathione reductase activities, as well as with increases in total and reduced glutathione content and lower Na+ accumulation in leaves. These results suggest that enhancement of antioxidant responses in Lj MG20 contributed to improve salt stress tolerance at early stages. On the other hand, after long-term high NaCl stress treatment, L. filicaulis exhibited lower biomass reduction, lower oxidative damage and Na+ accumulation in leaves than the control treatment; hence, this genotype was considered salt-tolerant. These apparently ambiguous results remark that salt tolerance, as a development-related process, was differentially expressed among the Lotus genotypes and depended on stress duration and plant phenological stage. 相似文献
8.
Gentile MA Melchiorre S Emolo C Moschioni M Gianfaldoni C Pancotto L Ferlenghi I Scarselli M Pansegrau W Veggi D Merola M Cantini F Ruggiero P Banci L Masignani V 《The Journal of biological chemistry》2011,286(16):14588-14597
Streptococcus pneumoniae expresses on its surface adhesive pili, involved in bacterial attachment to epithelial cells and virulence. The pneumococcal pilus is composed of three proteins, RrgA, RrgB, and RrgC, each stabilized by intramolecular isopeptide bonds and covalently polymerized by means of intermolecular isopeptide bonds to form an extended fiber. RrgB is the pilus scaffold subunit and is protective in vivo in mouse models of sepsis and pneumonia, thus representing a potential vaccine candidate. The crystal structure of a major RrgB C-terminal portion featured an organization into three independently folded protein domains (D2-D4), whereas the N-terminal D1 domain (D1) remained unsolved. We have tested the four single recombinant RrgB domains in active and passive immunization studies and show that D1 is the most effective, providing a level of protection comparable with that of the full-length protein. To elucidate the structural features of D1, we solved the solution structure of the recombinant domain by NMR spectroscopy. The spectra analysis revealed that D1 has many flexible regions, does not contain any intramolecular isopeptide bond, and shares with the other domains an Ig-like fold. In addition, we demonstrated, by site-directed mutagenesis and complementation in S. pneumoniae, that the D1 domain contains the Lys residue (Lys-183) involved in the formation of the intermolecular isopeptide bonds and pilus polymerization. Finally, we present a model of the RrgB protein architecture along with the mapping of two surface-exposed linear epitopes recognized by protective antisera. 相似文献
9.
R. M. Ulloa G. C. Mac Intosh M. Melchiorre A. N. Mentaberry P. Dallari D. N. Moriconi M. T. Téllez-Iñón 《Plant cell reports》1997,16(6):426-429
In vitro culture was used to study morphogenetic aspects of the tuberization process under controlled conditions in potato (Solanum tuberosum L.) plants. This paper accurately defines four stages of tuber development and their correlation to external morphological characteristics and histological structures. Protein kinase activity, assayed in each stage using Historic HAS as substrate, was differentially expressed during the tuberization process. Phosphorylation was maximum in the first stages of tuber formation. The incorporation of [32PO4
–1] to endogenous peptides containing serine/threonine amino acidic residues followed the same pattern that the protein kinase activity did.Abbreviations EDTA
Ethylenediaminetetraacetic acid
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EGTA
ethylenebis (oxyethylenenitrilo) tetraacetic acid
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MOPS
4-morpholine-propanesulfonic acid 相似文献
10.
Mariana Melchiorre Germán Robert Victorio Trippi Roberto Racca H. Ramiro Lascano 《Plant Growth Regulation》2009,57(1):57-68
In previous works, we have established a correlation between antioxidant system response and tolerance to drought, osmotic
stress and photooxidative stress of different wheat cultivars with contrasting drought tolerance. In the present work, a protocol
to obtain and transform wheat protoplasts was established. Transgenic protoplasts with Manganese Superoxide Dismutase (Mn-SOD)
(E.C.: 1.15.1.1) and Glutathione Reductase (GR) (E.C.: 1.6.4.2) overexpression in chloroplasts were obtained, and their responses
to photooxidative stress were characterized. Protoplasts with Mn-SOD or GR overexpression, showed different responses and
tolerance to photooxidative stress. Protoplasts with Mn-SOD overexpression showed lower levels of oxidative damage, higher
level of endogenous hydrogen peroxide and a great induction of total SOD and GR activities during photooxidative treatments.
In protoplasts with GR overexpression the oxidative damage provoked by the photooxidative treatment was similar to control
protoplasts, the GSH content and GSH/GSH + GSSG ratio were higher than control and Mn-SOD transformed protoplast, and total
SOD and GR activities were not induced. Our results suggest that the differential responses and tolerance to photooxidative
stress given by Mn-SOD or GR overexpression, also depend on the effects of these enzyme activities over the cellular redox
state balance, which modulate the responses to photooxidative stress. 相似文献