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331.
The sequence-specific assignment of the 1H-NMR spectrum of an enzyme, horse-muscle acylphosphatase 总被引:1,自引:0,他引:1
V Saudek J Boyd R J Williams M Stefani G Ramponi 《European journal of biochemistry》1989,182(1):85-93
A complete range of two-dimensional NMR experiments was used for the assignment of the 1H-NMR spectrum of horse muscle acylphosphatase. Firstly the spin systems of some easily identifiable amino acid side chains were assigned. These side chains involved all the aromatic residues and all the leucine, valine, isoleucine, threonine, alanine, proline as well as some of the glycine residues. Analysis of nuclear Overhauser enhancement spectra in our previous work had identified the sequential and long-range patterns characteristics for secondary structure elements. This result had also provided the identification of the main-chain alpha and amide proton resonances. Several of the completely assigned spin systems were then identified as being part of the secondary structure units which led, after analysis of the primary amino acid sequence, to unambiguous sequence-specific assignments. The identification and assignment of the remaining side-chain resonances was then completed and are reported here. These results provide a complete data base for the three-dimensional structure determination of this enzyme in solution. 相似文献
332.
Decay of the slow calcium current in twitch muscle fibers of the frog is influenced by intracellular EGTA 总被引:8,自引:3,他引:5
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The mechanism(s) of the decay of slow calcium current (ICa) in cut twitch skeletal muscle fibers of the frog were studied in voltage-clamp experiments using the double vaseline-gap technique. ICa decay followed a single exponential in 10 mM external Ca2+ and 20 mM internal EGTA solutions in all pulse protocols tested: single depolarizing pulses (activation protocol), two pulses (inactivation protocol), and during a long pulse preceded by a short prepulse (400 ms) to 80 mV (tail protocol). In single pulses the rate constant of ICa decay was approximately 0.75 s-1 at 0 mV and became faster with larger depolarizations. ICa had different amplitudes during the second pulses of the inactivation protocol (0 mV) and of the tail protocol (-20 to 40 mV) and had similar time constants of decay. The time constant of decay did not change significantly at each potential after replacing 10 mM Ca2+ with a Ca2+-buffered solution with malate. With 70 mM intracellular EGTA and 10 mM external Ca2+ solutions, ICa also decayed with a single-exponential curve, but it was about four times faster (approximately 3.5 s-1 at 0 mV pulse). In these solutions the rate constant showed a direct relationship with ICa amplitude at different potentials. With 70 mM EGTA, replacing the external 10 mM Ca2+ solution with the Ca2+-buffered solution caused the decay of ICa to become slower and to have the same relationship with membrane potential and ICa amplitude as in fibers with 20 mM EGTA internal solution. The mechanism of ICa decay depends on the intracellular EGTA concentration: (a) internal EGTA (both 20 and 70 mM) significantly reduces the voltage dependence of the inactivation process and (b) 70 mM EGTA dramatically increases the rate of tubular calcium depletion during the flow of ICa. 相似文献
333.
Relationship between myoplasmic calcium transients and calcium currents in frog skeletal muscle 总被引:3,自引:3,他引:0
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Ca2+ currents (ICa) and myoplasmic Ca2+ transients were simultaneously recorded in single muscle fibers from the semitendinosus muscle of Rana pipiens. The vaseline-gap voltage-clamp technique was used. Ca2+ transients were recorded with the metallochromic indicator dye antipyrylazo III. Ca2+ transients consisted of an early fast rising phase followed by a late slower one. The second phase was increased by experimental maneuvers that enlarged ICa, such as augmenting [Ca2+]o (from 2 to 10 mM) or adding (-)-Bay K 8644 (2 microM). When [Ca2+]o was increased, the second phase of the Ca2+ transients and ICa showed an average increase at 0 mV of 2 +/- 0.9 microM (4) and 1.4 +/- 0.3 mA/ml (4), respectively. (-)-Bay K 8644 increased the late phase of the Ca2+ transients and ICa at 0 mV by 0.8 +/- 0.3 microM (3) and 6.7 +/- 2.0 mA/ml (4), respectively. The initial fast rising phase of the Ca2+ transients was not modified. (-)-Bay K 8644 slowed the time constant of decay of the transients by 57 +/- 6 ms. In other experimental conditions, Ca2+ release from the sarcoplasmic reticulum (SR) was impaired with repetitive stimulation in 1 mM [EGTA]i-containing fibers. Under those circumstances, Ca2+ transients directly followed the time integral of ICa. Pulses to 0 mV caused a large Ca2+ transient that became suppressed when large pulses to 100 mV were applied. In fibers with functioning SR, pulses to 100 mV elicited somewhat smaller or similar amplitude Ca2+ transients when compared with those elicited by pulses to 0 mV. The increase in ICa after raising [Ca2+]o or adding (-)-Bay K 8644 cannot directly explain the change in Ca2+ transients in fibers with functioning SR. On the other hand, when Ca2+ release from the SR is impaired Ca2+ transients depend on ICa. 相似文献
334.
Lutz Birnbaumer Ning Qin Riccardo Olcese Erwin Tareilus Daniela Platano Jim Costantin Enrico Stefani 《Journal of bioenergetics and biomembranes》1998,30(4):357-375
Calcium channel subunits have profound effects on how 1 subunits perform. In this article we summarize our present knowledge of the primary structures of subunits as deduced from cDNAs and illustrate their different properties. Upon co-expression with 1 subunits, the effects of subunits vary somewhat between L-type and non-L-type channels mostly because the two types of channels have different responses to voltage which are affected by subunits, such as long-lasting prepulse facilitation of 1C (absent in 1E) and inhibition by G protein dimer of 1E, absent in 1C. One subunit, a brain 2a splice variant that is palmitoylated, has several effects not seen with any of the others, and these are due to palmitoylation. We also illustrate the finding that functional expression of 1 in oocytes requires a subunit even if the final channel shows no evidence for its presence. We propose two structural models for Ca2+ channels to account for 1 alone channels seen in cells with limited subunit expression. In one model, dissociates from the mature 1 after proper folding and membrane insertion. Regulated channels seen upon co-expression of high levels of would then have subunit composition 1. In the other model, the chaperoning remains associated with the mature channel and 1 alone channels would in fact be 1 channels. Upon co-expression of high levels of the regulated channels would have composition [1]. 相似文献
335.
Gérard Landemore Pierre Stefani Michèle Quillec Pierre Lecoq-Guilbert Christian Billotte Jacques Izard 《The Histochemical journal》1999,31(3):161-167
To document the ultrastructural distribution of lens capsule proteoglycans, rabbit lens capsules were fixed and stained overnight in 50mM sodium acetate, pH 5.6, containing 2.5% glutaraldehyde, 0.2% Cuprolinic Blue and 0.2M MgCl2. They were rinsed, stained with 1% aqueous sodium tungstate, embedded in Epon, sectioned (60nm), and examined with an electron microscope at 60kV.Proteoglycan–Cuprolinic Blue complexes mainly appeared as networks of small electron-dense filaments throughout the posterior and anterior capsules. The posterior capsule was a single layer with a network of small proteoglycan filaments gradually decreasing in size from the humoral side (90×10nm) to the lenticular side (30×8nm). The humoral side of the anterior capsule had a thin lamina (400nm) containing large (180×40nm), very electron-dense proteoglycan–Cuprolinic Blue complexes plus small proteoglycans. Below this lamina, the complexes were only seen as filaments slightly smaller than those in the corresponding area of the posterior capsule.Cuprolinic Blue binding of the anterior and posterior lens capsules revealed differences in the size and distribution of their sulphated proteoglycans which do not correspond to the patterns of their immunoreactivity with anti-heparan sulphate proteoglycan. The humoral lamina in the anterior capsules, with large proteoglycan structures, might be a distinct structural and functional compartment. 相似文献
336.
Molecular evolution of the synapsin gene family 总被引:4,自引:0,他引:4
Kao HT Porton B Hilfiker S Stefani G Pieribone VA DeSalle R Greengard P 《The Journal of experimental zoology》1999,285(4):360-377
Synapsins, a family of synaptic vesicle proteins, play a crucial role in the regulation of neurotransmission and synaptogenesis. They have been identified in a variety of invertebrate and vertebrate species, including human, rat (Rattus norvegicus), cow (Bos taurus), longfin squid (Loligo pealei), and fruit fly (Drosophila melanogaster). Here, synapsins were cloned from three additional species: frog (Xenopus laevis), lamprey (Lampetra fluviatilis), and nematode (Caenorhabditis elegans). Synapsin protein sequences from all these species were then used to explore the molecular phylogeny of these important neuronal phosphoproteins. The ancestral condition of a single synapsin gene probably gave rise to the vertebrate synapsin gene family comprised of at least three synapsin genes (I, II, and III) in higher vertebrates. Synapsins possess multiple domains, which have evolved at different rates throughout evolution. In invertebrate synapsins, the most conserved domains are C and E. During the evolution of vertebrates, at least two gene duplication events are hypothesized to have given rise to the synapsin gene family. This was accompanied by the emergence of an additional conserved domain, termed A. J. Exp. Zool. ( Mol. Dev. Evol. ) 285:360-377, 1999. 相似文献
337.
338.
The phylogeographical pattern of vairone ( Telestes muticellus ) populations was assessed to test the biogeographical distinction of three peri-Mediterranean ichthyogeographical districts: Padano-Venetian (PV), Tuscano-Latium (TL) and southern France (SF), evaluating the role of Alpine and Apennine barriers in shaping distinct evolutionary lineages. A fragment of mitochondrial DNA (mtDNA) cytochrome b (cyt b ) was sequenced in 153 specimens from 14 north-western Italian populations, collected in 10 tributaries of Po River and in four rivers on the Tyrrhenian slope of Ligury, and 32 haplotypes were identified. The phylogenetic analyses confirmed the presence of two distinct clades, an 'Italian clade' ( T. muticellus ) and a 'French clade' ( T. souffia ), showing an average genetic distance of 12.9% (± 1.3 SD) and allopatric distribution. The Nested Clade Analysis (NCA) and the Analysis of Molecular Variance ( amova ) revealed an isolated gene pool in eastern basins on the Tyrrhenian slope of Ligury. The phylogeographical findings suggest: (i) the lack of permeability of Alpine barrier towards the dispersion across Italian and French hydrographical systems; and (ii) partial permeability of Mediterranean Alps and Apennines through river captures crossing lower watersheds. 相似文献
339.
da Costa Medina LF Viau CM Moura DJ Saffi J Stefani V Brandelli A Henriques JA 《Mutation research》2008,650(2):140-149
There are few studies on the biological activity of aminohydroxy derivates of 1,4-naphthoquinone (1,4-NQ) on prokaryotic and eukaryotic cells. We determined the mutagenic activity of 5-amino-8-hydroxy-1,4-naphthoquinone (ANQ) and 5-amino-2,8-dihydroxy-1,4-naphthoquinone (ANQ-OH) as compared to the unsubstituted 1,4-NQ in Salmonella/microsome assay. Potential mutagenic and recombinogenic effects and cytotoxicity were analyzed in haploid and diploid cultures of the yeast Saccharomyces cerevisiae. In Salmonella/microsome assay, 1,4-NQ was not mutagenic, whereas aminohydroxynaphthoquinones were weakly mutagenic in TA98 and TA102 strains. In haploid yeast in stationary growth phase (STAT), mutagenic response was only observed for the hom3 locus at the highest dose. In diploid yeast, aminohydroxynaphthoquinones did not induce any recombinogenic events, but 1,4-NQ was shown to be a recombinogenic agent. These results suggest that aminohydroxynaphthoquinones are weak mutagenic agents only in prokaryotic cells. The cytotoxicity of 1,4-NQ in yeast stationary cells was more significant in diploid cells as compared to that observed in haploid cells. However, ANQ and ANQOH were slightly cytotoxic in all treatments. Genotoxicity of these naphthoquinone compounds was also determined in V79 Chinese hamster lung fibroblast cells using standard Comet, as well as modified Comet assay with the bacterial enzymes formamidopyrimidine DNA-glycosylase (FPG) and endonuclease III (ENDOIII). Both 1,4-NQ and ANQ induced pronounced DNA damage in the standard Comet assay. The genotoxic effect of ANQ-OH was observed only at the highest dose. In presence of metabolic activation all substances showed genotoxic effects on V79 cells. Post-treatment of V79 cells with ENDOIII and FPG proteins did not have a significant effect on ANQ-OH-induced oxidative DNA damage as compared to standard alkaline Comet assay. However, all naphthoquinones were genotoxic in V79 cells in the presence of metabolic activation and post-treatment with enzymes, indicating that all compounds induced oxidative DNA damage in V79 cells. Our data suggest that aminohydroxynaphthoquinone pro-oxidant activity, together with their capability of DNA intercalation, have an important role in mutagenic and genotoxic activities. 相似文献
340.
Gomes P Saito T Del Corsso C Alioua A Eghbali M Toro L Stefani E 《Biochimica et biophysica acta》2008,1783(10):1884-1892
Voltage-gated K(+) (Kv) channels are key determinants of cardiac and neuronal excitability. A substantial body of evidence has accumulated in support of a role for Src family tyrosine kinases in the regulation of Kv channels. In this study, we examined the possibility that c-Src tyrosine kinase participates in the modulation of the transient voltage-dependent K(+) channel Kv4.3. Supporting a mechanistic link between Kv4.3 and c-Src, confocal microscopy analysis of HEK293 cells stably transfected with Kv4.3 showed high degree of co-localization of the two proteins at the plasma membrane. Our results further demonstrate an association between Kv4.3 and c-Src by co-immunoprecipitation and GST pull-down assays, this interaction being mediated by the SH2 and SH3 domains of c-Src. Furthermore, we show that Kv4.3 is tyrosine phosphorylated under basal conditions. The functional relevance of the observed interaction between Kv4.3 and c-Src was established in patch-clamp experiments, where application of the Src inhibitor PP2 caused a decrease in Kv4.3 peak current amplitude, but not the inactive structural analogue PP3. Conversely, intracellular application of recombinant c-Src kinase or the protein tyrosine phosphatase inhibitor bpV(phen) increased Kv4.3 peak current amplitude. In conclusion, our findings provide evidence that c-Src-induced Kv4.3 channel activation involves their association in a macromolecular complex and suggest a role for c-Src-Kv4.3 pathway in regulating cardiac and neuronal excitability. 相似文献