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Query: UNIPROT:Q86TM3 (cage)
 29,987 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Of three sets of Djungarian dwarf hamster, two groups were raised during winter under greatly differing circumstances. One winter group was raised within a climate controlled cage in which the ambient temperature was maintained at 22 degrees C and whereby conditions of light vs darkness were maintained in a constant 12 hr cycle. The second winter group was raised out of doors whereby the hamsters were subjected to prevailing seasonal environmental conditions. A third group was studied under summer conditions, as well. Ca(2+)-, Mg(2+)- and (Ca2+/Mg2+)-ATPase activity was analysed in cellular (= total homogenate) and subcellular fractions (P1-, synaptosomal fraction, synaptic membranes) from cortex, cerebellum and basal brain. 2. The data obtained indicate similar ATPase activity in the cortical homogenates of the winter indoor and summer hamsters. 3. Winter outdoor animals experiencing normal torpidity, however, exhibited reduced ATPase activity by about 50%. 4. Cortical subcellular fractions yielded different results: both the winter and the summer groups showed high ATPase activity in the synaptosomal and synaptic membrane fractions. 5. In the total cerebellar homogenate, the hamsters raised under summer and winter conditions showed the greatest enzyme activity, although less activity was seen in the subcellular fractions. 6. The ATPase activity in the basal brain was found to be nearly identical in all three hamster groups.
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PMID:Brain Ca2+/Mg(2+)-ATPase activity and seasonal adaptation of the Djungarian dwarf hamster Phodopus sungorus. 168 89

The photosensitized monomerization of the cyclobutane dimers of 1,3-dimethylthymine by p-chloranil was investigated by means of steady-state irradiation and laser-flash photolysis. Quantum yields for the monomerization are 0.34 for the cis,syn dimer, 0.39 for the trans,syn dimer, and much less than 10(-2) for the cis,anti isomer. Formation of the chloranil anion radical associated with quenching of triplet chloranil by the dimers demonstrates that electron transfer from dimers to triplet chloranil occurs to initiate the monomerization. Kinetic analysis suggested that the syn-dimer cation radicals undergo the ring cleavage at greater than or equal to 10(9) s-1 before escaping from the solvent cage, while the reactivity of the anti-dimer cation radical is very low. The different reactivities of the syn and anti dimer cation radicals are discussed in terms of through-bond coupling between the n orbitals of N(1) and N(1') involving the cyclobutane-ring sigma orbitals. In the cases of the syn-dimers, the sensitizer-dimer ion-radical pairs undergo the rapid geminate recombination that works as a major energy dissipating channel responsible for the lower-than-unity quantum yields. It has been found that the presence of Mg(ClO4)2 at 0.1 M enhances approximately 1.5 times either the monomerization of the syn dimers or the formation of the chloranil anion radical. A laser-flash photolysis study shows that Mg2+ forms a complex with either the triplet or the anion radical of chloranil. The net salt effects are attributed to the retardation of the rapid geminate recombination by the participation of Mg2+ in the sensitizer-dimer ion-radical pairs.
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PMID:Chloranil-photosensitized monomerization of dimethylthymine cyclobutane dimers and effect of magnesium perchlorate. 196 58

Since we have demonstrated that ATPase system was sensitive to chlordecone, it was decided to examine the relationship between physiological and biochemical responses to this neurotoxin. Male Sprague-Dawley rats were fed with chlordecone by gastric intubation at 10, 25 and 50 mg/kg/day for three days. Control rats received 0.3 ml of corn oil. Complete body movements (including tremors) were monitored for a period of 12 hr at 24, 48 and 72 hr after treatment by a piezoelectric crystal attached to the bottom of a plastic rodent cage. The output of the crystal was recorded by a Grass model of EEG machine and magnetic tape. For biochemical study chlordecone treated rats were killed, the brain synaptosomes were prepared and Na+-K+ ATPase, oligomycin-sensitive and insensitive Mg2+ ATPases were determined. Rats receiving chlordecone showed an increased tremor activity which was significant and dose- dependent with a correlation coefficient of the regression line of 0.96. The onset of tremors was evident as early as 2 hr in 50 mg/kg dosed rats. Behavioral abnormalities include startling response to external stimuli like sound, etc. The brain synaptosomal Na+-K+ and oligomycin-sensitive Mg2+ ATPases were significantly decreased in chlordecone treated rats as compared to controls and the decrease was dose-dependent. A linear relationship was observed between the decreases in ATPase activities and physiological (tremor) activity with an r value of 0.96. These results suggest that the inhibition of ATPase system in brain may be related to the production of the neurotoxic symptoms.
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PMID:Acute chlordecone toxicity in rats: a relationship between tremor and ATPase activities. 617 57

Phosphatidic acid can act as Ca2+ cross-membrane ionophore without the necessity of previous autoxidation. The apparent PA-CA2+ dissociation constant is 3 X 10(-3), i.e., in the range of extracellular Ca2+ concentration. There is at least 100-fold preference for Ca2+ over Mg2+. Ca2+ transfer rates are proportional to the square of phosphatidic acid concentration in the bilayer. Removal of the fatty acid ester CO groups reduces the Ca2+ ferrying rate by more than 90 percent. It appears that the cation is held in a cage formed by phosphate and carbonyl oxygens of two PA molecules. In this coordination complex both Ca2+ and the phosphatidic acid headgroups are dehydrated, and the Ca(phosphatide)2 assembly becomes lipid-soluble and can traverse the bilayer.
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PMID:Ca(phosphatidate)2 can traverse liposomal bilayers. 648 61

The basal body cage is a fibrillar chamber which surrounds each basal body in the ciliate cytoskeleton. The function of this chamber is unknown. In Tetrahymena, the cage contains actin filaments which connect the cage to triplet microtubules. In this study, we have examined the cage for the presence of myosin. Skeletal muscle myosin-II heavy and light chains were used to affinity-purify anti-MHC and anti-MLC antibodies, respectively, from an antiserum raised against Tetrahymena oral apparatus proteins. On western immunoblots of ATP-solubilized Tetrahymena proteins, the anti-MHC antibody detected a putative myosin heavy (180 kDa) chain, and the anti-MLC antibody detected a putative myosin light (18 kDa) chain. The anti-MHC antibody specifically labeled the AI zone of sarcomeres. In cosedimentation assays with an ATP-solubilized protein fraction, the 180 kDa polypeptide associated with skeletal muscle actin filaments in an ATP-dependent manner. The sedimented actin filaments appeared to be organized into bundles. Immunodepletion of the 180 kDa rendered the ATP-solubilized protein fraction ineffective in bundling actin filaments in a cosedimentation assay. ATP-solubilized Tetrahymena proteins, which included the 180 kDa polypeptide, exhibited F-actin-stimulated, Mg2+ ATPase activity and K+, EDTA ATPase activity which are characteristic of myosin ATPases. Immunodepletion of the 180 kDa polypeptide reduced the F-actin, Mg2+ ATPase activity of the ATP-solubilized protein fraction by more than 80%. Based on these various observations, we conclude that the 180 kDa polypeptide is a putative myosin heavy chain, probably a myosin-II and that the 18 kDa polypeptide is probably a myosin-II light chain. We have used the affinity-purified, anti-myosin antibodies with immunofluorescence microscopy and immunogold electron microscopy to map the location of the putative myosin heavy and light chains in Tetrahymena. Immunofluorescence microscopy showed that the anti-myosin antibodies localized to Tetrahymena somatic and oral region basal bodies. At the ultrastructural level, the anti-myosin antibodies localized to filaments in the basal body-cage complex. The labeling patterns with both anti-myosin antibodies were identical to the labeling pattern observed with an anti-actin antibody reported in a previous study. The co-localization of myosin and actin argue for a motility system within the basal body-cage complex.
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PMID:Putative myosin heavy and light chains in Tetrahymena: co-localization to the basal body-cage complex and association of the heavy chain with skeletal muscle actin filaments in vitro. 762 16

Astrocytes exhibit a form of excitability and communication on the basis of intracellular Ca2+ variations (Cornell-Bell et al., 1990; Charles et al., 1991) that can be initiated by neuronal activity (Dani et al., 1992; Porter and McCarthy, 1996). A Ca2+ elevation in astrocytes induces the release of glutamate (Parpura et al., 1994; Pasti et al., 1997; Araque et al., 1998;Bezzi et al., 1998), which evokes a slow inward current in neurons and modulates action potential-evoked synaptic transmission between cultured hippocampal cells (Araque et al., 1998), suggesting that astrocytes and neurons may function as a network with bidirectional communication. Here we show that a Ca2+ elevation in astrocytes increases the frequency of excitatory as well as inhibitory miniature postsynaptic currents (mPSCs), without modifying their amplitudes. Thapsigargin incubation, microinjection of the Ca2+ chelator BAPTA, and photolysis of the Ca2+ cage NP-EGTA demonstrate that a Ca2+ elevation in astrocytes is both necessary and sufficient to modulate spontaneous transmitter release. This Ca2+-dependent release of glutamate from astrocytes enhances mPSC frequency by acting on NMDA glutamate receptors, because it is antagonized by D-2-amino-5-phosphonopentanoic acid (AP5) or extracellular Mg2+. These NMDA receptors are located extrasynaptically, because blockage specifically of synaptic NMDA receptors by synaptic activation in the presence of the open channel blocker MK-801 did not impair the AP5-sensitive astrocyte-induced increase of mPSC frequency. Therefore, astrocytes modulate spontaneous excitatory and inhibitory synaptic transmission by increasing the probability of transmitter release via the activation of NMDA receptors.
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PMID:Calcium elevation in astrocytes causes an NMDA receptor-dependent increase in the frequency of miniature synaptic currents in cultured hippocampal neurons. 971 53

We report efficient two-photon and UV-laser flash photolysis of dimethoxynitrophenyl-EGTA-4 (DMNPE-4), a newly-developed photolabile Ca(2+)-specific chelator. This compound exhibits good two-photon absorption at 705 nm, has a low Mg2+ affinity (approximately 7 mM), a Kd for Ca2+ of 19 nM, a quantum yield of 0.20 and changes its Ca2+ affinity by 21,000-fold upon photolysis. Two-photon excitation photolysis (TPP) experiments were performed with a Ti:Sapphire laser in solutions containing DMNPE-4 with either 0 or 10 mM Mg2+ and compared to that of the widely used Ca2+ cage, DM-nitrophen (Kd for Ca2+ 5 nM, Kd for Mg2+ 2.5 microM, quantum yield 0.18, affinity change 600,000-fold). The resulting Ca2+ signals were recorded with the fluorescent Ca2+ indicator fluo-3 and a laser-scanning confocal microscope in the line-scan mode. In vitro, photolysis of DMNPE-4:Ca2+ produced Ca(2+)-release signals that had comparable amplitudes and time courses in the presence and absence of Mg2+. However, photorelease of Ca2+ from DM-nitrophen was obviated by the presence of Mg2+. In patch-clamped isolated cardiac myocytes, equivalent TPP results were obtained in analogous experiments. Single-photon excitation of DMNPE-4 by Nd:YAG laser flashes produced Na-Ca exchange currents of comparable amplitude in the absence and presence of Mg2+. However, only very small currents were observed in DM-nitrophen solution containing 10 mM Mg2+. In conclusion, both DMNPE-4 and DM-nitrophen undergo TPP, however, only DMNPE-4 exhibits efficient release of Ca2+ in the presence of Mg2+.
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PMID:Two-photon and UV-laser flash photolysis of the Ca2+ cage, dimethoxynitrophenyl-EGTA-4. 1019 63

Trypanosomatids have a striking cage-like arrangement of submembraneous microtubules. We previously showed that alpha- and beta- tubulins of these stable microtubules are extensively modified by polyglutamylation. Cytoskeletal microtubular preparations obtained by Triton extraction of Leishmania tarentolae and Crithidia fasciculata retain an enzymatic activity that incorporates radioactive glutamic acid in a Mg2+-ATP-dependent manner into alpha- and beta-tubulins. The tubulin polyglutamylase is extracted by 0.25 M salt. The Crithidia enzyme can be purified by ATP-affinity chromatography, glycerol-gradient centrifugation and ion-exchange chromatography. After extraction from the microtubular cytoskeleton the glutamylase forms a complex with alphabeta tubulin, but behaves after removal of tubulin as a globular protein with a molecular mass of 38x10(3). In highly enriched fractions a corresponding band is the major polypeptide visible in SDS-PAGE. The enzyme from Crithidia recognises mammalian brain tubulin, where it incorporates glutamic acid preferentially into the more acidic variants of both alpha- and beta-tubulins. Synthetic peptides with an oligoglutamyl side chain, corresponding to the carboxy-terminal end of brain alpha- and beta-tubulins, are accepted by the enzyme, albeit at low efficiency. The polyglutamylase elongates the side chain by up to 3 and 5 residues, respectively. Other properties of the tubulin polyglutamylase are also discussed.
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PMID:Isolation of tubulin polyglutamylase from Crithidia; binding to microtubules and tubulin, and glutamylation of mammalian brain alpha- and beta-tubulins. 1036 48

The chaperonin HSP60 (GroEL) proteins are essential in eubacterial genomes and in eukaryotic organelles. Functional regions inferred from mutation studies and the Escherichia coli GroEL 3D crystal complexes are evaluated in a multiple alignment across 43 diverse HSP60 sequences, centering on ATP/ADP and Mg2+ binding sites, on residues interacting with substrate, on GroES contact positions, on interface regions between monomers and domains, and on residues important in allosteric conformational changes. The most evolutionary conserved residues relate to the ATP/ADP and Mg2+ binding sites. Hydrophobic residues that contribute in substrate binding are also significantly conserved. A large number of charged residues line the central cavity of the GroEL-GroES complex in the substrate-releasing conformation. These span statistically significant intra- and inter-monomer three-dimensional (3D) charge clusters that are highly conserved among sequences and presumably play an important role interacting with the substrate. Unaligned short segments between blocks of alignment are generally exposed at the outside wall of the Anfinsen cage complex. The multiple alignment reveals regions of divergence common to specific evolutionary groups. For example, rickettsial sequences diverge in the ATP/ADP binding domain and gram-positive sequences diverge in the allosteric transition domain. The evolutionary information of the multiple alignment proffers attractive sites for mutational studies.
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PMID:Conservation among HSP60 sequences in relation to structure, function, and evolution. 1075 9

Reactions of MnX2.nH2O with tris(N-(D-mannosyl)-2-aminoethyl)amine ((D-Man)3-tren), which was formed from D-mannose and tris(2-aminoethyl)amine (tren) in situ, afforded colorless crystals of [Mn((D-Man)3-tren)]X2 (3a, X = Cl; 3b, X = Br; 3c, X = NO3; 3d, X = 1/2SO4). The similar reaction of MnSO4.5H2O with tris(N-(L-rhamnosyl)-2-aminoethyl)amine ((L-Rha)3-tren) gave [Mn((L-Rha)3-tren)]SO4 (4d), where L-rhamnose is 6-deoxy-L-mannose. The structures of 3b and 4d were determined by X-ray crystallography to have a seven-coordinate Mn(II) center ligated by the N-glycoside ligand, (aldose)3-tren, with a C3 helical structure. Three D-mannosyl residues of 3b are arranged in a delta(ob3) configuration around the metal, leading to formation of a cage-type sugar domain in which a water molecule is trapped. In 4d, three L-rhamnosyl moieties are in a delta(lel3) configuration to form a facially opened sugar domain on which a sulfate anion is capping through hydrogen bonding. These structures demonstrated that a configurational switch around the seven-coordinate manganese(II) center occurs depending on its counteranion. Reactions of 3a, 3b, and 4d with 0.5 equiv of Mn(II) salt in the presence of triethylamine yielded reddish orange crystals formulated as [[Mn((aldose)3-tren)]2Mn(H2O)X3.nH2O (5a, aldose = D-Man, X = Cl; 5b, aldose = D-Man, X = Br; 6d, aldose = L-Rha, X = 1/2SO4). The analogous trinuclear complexes 6a (aldose = L-Rha, X = Cl), 6b (aldose = L-Rha, X = Br), and 6c (aldose = L-Rha, X = NO3) were prepared by the one-pot reaction of Mn(II) salts with (L-Rha)3-tren without isolation of the intermediate Mn(II) complexes. X-ray crystallographic studies revealed that 5a, 5b, 6c, and 6d have a linearly ordered trimanganese core, Mn(II)Mn(III)Mn(II), bridged by two carbohydrate residues with Mn-Mn separations of 3.845(2)-3.919(4) A and Mn-Mn-Mn angles of 170.7(1)-173.81(7) degrees. The terminal Mn(II) atoms are seven-coordinate with a distorted mono-face-capped octahedral geometry ligated by the (aldose)3-tren ligand through three oxygen atoms of C-2 hydroxyl groups, three N-glycosidic nitrogen atoms, and a tertiary amino group. The central Mn(III) atoms are five-coordinate ligated by four oxygen atoms of carbohydrate residues in the (aldose)3-tren ligands and one water molecule, resulting in a square-pyramidal geometry. In the bridging part, a beta-aldopyranosyl unit with a chair conformation bridges the two Mn(II)Mn(III) ions with the C-2 mu-alkoxo group and with the C-1 N-glycosidic amino and the C-3 alkoxo groups coordinating to each metal center. These structures could be very useful information in relation to xylose isomerases which promote aldose-ketose isomerization by using divalent dimetal centers such as Mn2+, Mg2+, and Co2+.
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PMID:Novel Mn(II)Mn(III)Mn(II) trinuclear complexes with carbohydrate bridges derived from seven-coordinate manganese(II) complexes with N-glycoside. 1127 63


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