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1.
Thed mutagenic activities of 11 N-methyl-N′-alkyl-N-nitrosoureas were tested on Samonellatyphimurium TA1535 and compared with chemical properties (alkylating activity and decompostion rate). In their relative mutagenicities the N-nitrosoureas that had a cyclic N′-alkyl group showed far more mutagenic activity than those having a chain N′-alkyl group. M(1-A)NU and M(2-A)NU, which had the most bulky N′-alkyl group in this series, exhibited lethal effects at high concentrations. The mutagenicity showed a small positive correlation with decomposition rates but not with alkylating activities on 4-(p-nitrobenzyl_prridine. The highest mutagenicity in this series was observed in N-methyl-N′-cyclobutyl-N-nitrosourea.These results suggest that, in this series of N-methyl-M′-alkyl-N-nitrosoureas, structural differences in the N′-alkyl groups had great significance in mutagenicity. 相似文献
2.
The mutagenicity of N-methyl-N′-nitro-N-nitrosoguanidine to Salmonella typhimurium hisG46 was enhanced by pre-incubating the chemical with bacteria in sodium phosphate buffer. Addition of glucose (to 15 mM) to the pre-incubation mixture further enhanced the mutagenicity. Pre-incubation with glucose also increased the mutagenicity of N-methyl-N-nitrosourea. Fructose, galactose, pyruvate and succinate also enhanced the mutagenicity of N-methyl-N′-nitro-N-nitrosoguanidine. The effect of glucose was observed with S. typhimurium strains hisG46, TA1975, TA1950, TA1535 and TA100. 相似文献
3.
Pingyang Liu Michael P. Torrens-Spence Haizhen Ding Bruce M. Christensen Jianyong Li 《Amino acids》2013,44(2):391-404
Animal aspartate decarboxylase (ADC), glutamate decarboxylase (GDC) and cysteine sulfinic acid decarboxylase (CSADC) catalyze the decarboxylation of aspartate, glutamate and cysteine sulfinic acid to β-alanine, γ-aminobutyric acid and hypotaurine, respectively. Each enzymatic product has been implicated in different physiological functions. These decarboxylases use pyridoxal 5-phosphate (PLP) as cofactor and share high sequence homology. Analysis of the activity of ADC in the presence of different amino determined that beta-alanine production from aspartate was diminished in the presence of cysteine. Comparative analysis established that cysteine also inhibited GDC and CSADC in a concentration-dependent manner. Spectral comparisons of free PLP and cysteine, together with ADC and cysteine, result in comparable spectral shifts. Such spectral shifts indicate that cysteine is able to enter the active site of the enzyme, interact with the PLP-lysine internal aldimine, form a cysteine-PLP aldimine and undergo intramolecular nucleophilic cyclization through its sulfhydryl group, leading to irreversible ADC inactivation. Cysteine is the building block for protein synthesis and a precursor of cysteine sulfinic acid that is the substrate of CSADC and therefore is present in many cells, but the presence of cysteine (at comparable concentrations to their natural substrates) apparently could severely inhibit ADC, CSADC and GDC activity. This raises an essential question as to how animal species prevent these enzymes from cysteine-mediated inactivation. Disorders of cysteine metabolism have been implicated in several neurodegenerative diseases. The results of our study should promote research in terms of mechanism by which animals maintain their cysteine homeostasis and possible relationship of cysteine-mediated GDC and CSADC inhibition in neurodegenerative disease development. 相似文献
4.
Constant Gielens Guido Maes Thérèse Zeegers-Huyskens René Lontie 《Journal of inorganic biochemistry》1980,13(1):41-47
Resonance Raman spectra were recorded for tenth molecules of βC-haemocyanin of Helix pomatia, for a limited tryptic hydrolysate, and for the five isolated fragments.On excitation at 514.5 nm the intensity of the peroxide stretching vibration was preserved in the fragments. Domain h showed a frequency of 741 cm?1 in contrast to 745–747 cm?1 for the other fragments.On excitation at 457.9 nm the intensity of the Cu-N vibration at 270 cm?1 was lowered on partial trypsinolysis, suggesting a less symmetrical arrangement of the ligands of Cu in the fragments. 相似文献
5.
The general pathology induced by δ-endotoxin in terms of larval behavior and hemolymph chemistry has been widely studied in the so-called Type I insect, Bombyx mori. The succession of symptoms is divided into four arbitrary stages: Stage 0, appearance and locomotion normal, no feeding; Stage 1, slightly sluggish; Stage 2, extremely sluggish; and Stage 3, complete paralysis. The action of δ-endotoxin is highly specific to the midgut since contractile movement of both foregut and hindgut continues long after all locomotor activity and heartbeat have stopped. Immediately after the silkworm stops feeding and blood pH sharply rises, there is an associated abrupt rise in the K+ concentration of hemolymph. Thereafter, the rise in K+ is linear while the rise in pH is not. In vivo measurements have not yielded the same simple linear dependence of pH on K+ concentrations that is found in in vitro mixtures of hemolymph and midgut juice. Ligation experiments showed that the same pathological sequence (rise of pH and K+ concentration, and general paralysis) follows whether the toxin has unrestricted access to the entire midgut or only part of it (anterior or posterior). From the results of injections of midgut juice or various salt solutions into hemocoel, we came to the conclusions that the blood pH and the symptoms are not necessarily parallel and the intact midgut and Malpighian tubules have strong functions for ion regulation. 相似文献
6.
Hughes AL 《Immunogenetics》2012,64(7):549-558
The βGRP/GNBP/β-1,3-glucanase protein family of insects includes several proteins involved in innate immune recognition, such as the β-glucan recognition proteins of Lepidoptera and the Gram-negative bacteria-binding proteins of Drosophila. A phylogenetic analysis supported the existence of two distinct subfamilies, designated the pattern recognition receptor (PRR) and glucanase subfamilies, which originated by gene duplication prior to the origin of the Holometabola. In the C-terminal region (CTR) shared by both subfamilies, the PRR subfamily has evolved significantly more rapidly at the amino acid sequence level than has the glucanase subfamily, implying a relative lack of constraint on the amino acid sequence of this region in the PRR subfamily. PRR subfamily members also include an N-terminal region (NTR), involved in carbohydrate recognition, which is not shared by glucanase subfamily members. In comparisons between paralogous PRR subfamily members, there were no conserved amino acid residues in the NTR. However, when pairs of putatively orthologous PRR subfamily members were compared, the NTR was most often as conserved as the CTR or more so. This pattern suggests that the NTR may be important in functions specific to the different paralogs, while amino acid sequence changes in the NTR may have been important in functional differentiation among paralogs, specifically with regard to the types of carbohydrates that they recognize. 相似文献
7.
《Gene》1996,172(1):155-159
The β-catenin/plakoglobin/armadillo gene family encodes a group of highly conserved proteins which play important roles in cadherin-mediated cell adhesion and in signal transduction mechanisms involved in regulating development. This gene family previously had been isolated only from higher metazoans. Here, we describe the isolation and characterization of a β-catenin (βCtn) homologue from Hydra magnipapillata a diploblastic lower metazoan. Comparison of the putative amino acid (aa) sequence of Hydra βCtn, with its homologues in higher metazoans, shows that a repeating 42-aa motif present in its central domain is highly conserved throughout the metazoa. This suggests that βCtn appeared very early in metazoan evolution, possibly when primitive multicellular animals started to form epithelial cell layers. 相似文献
8.
Susan Peacock Nathan Brot Herbert Weissbach 《Biochemical and biophysical research communications》1983,113(3):1018-1025
Using the plasmid pNF1337 as template, a mRNA preparation has been obtained that directs the synthesis of fMet-Val, the N-terminal dipeptide of the β subunit of RNA polymerase. RNA polymerase holoenzyme specifically inhibits the mRNA-directed synthesis of fMet-Val showing that the autoregulation by RNA polymerase of β,β′ synthesis is at the level of translation. L factor ( gene product) stimulates the synthesis of fMet-Val from a DNA template but not from mRNA. Rifampicin has no effect on the mRNA-directed synthesis of fMet-Val or the ability of RNA polymerase to inhibit fMet-Val synthesis. 相似文献
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10.
The symbionts of the macronuclei of Paramecium bursaria and P. caudatum, “Holospora curviuscula” 02AZ16 and H. obtusa 88Ti, respectively, were obtained and investigated. The 16S rDNA nucleotide sequences of “Holospora curviuscula” were obtained for the first time. The differences in 16S rDNA (3.4%) suggest their classification within the genus Holospora. Molecular phylogenetic analysis of the symbionts revealed that these intranuclear symbionts of the ciliates belonged to
the order Rickettsiales, forming within a compact cluster of related species. 相似文献
11.
F1-ATPase is an ATP-driven motor in which γε rotates in the α3β3-cylinder. It is attenuated by MgADP inhibition and by the ε subunit in an inhibitory form. The non-inhibitory form of ε subunit of thermophilic Bacillus PS3 F1-ATPase is stabilized by ATP-binding with micromolar Kd at 25 °C. Here, we show that at [ATP] > 2 μM, ε does not affect rotation of PS3 F1-ATPase but, at 200 nM ATP, ε prolongs the pause of rotation caused by MgADP inhibition while the frequency of the pause is unchanged. It appears that ε undergoes reversible transition to the inhibitory form at [ATP] below Kd. 相似文献
12.
The control of field tuber dormancy in the yam (Dioscorea cayenensis–D. rotundata complex) is poorly understood. Although studies have examined single environmental factors and chemical treatments that might prolong tuber dormancy and storage, only a few were focused on further tuber sprouting. The present study concerns microtubers obtained by in vitro culture. When microtubers were harvested (after 9 months of culture) and directly transferred on a new medium without hormones, the tubers rapidly sprouted in in vitro conditions. No dormancy was observed in this case. Harvested microtubers were also stored dry in jars in sterile conditions during 2 to 18 weeks before in vitro sprouting. In this case, microtubers stored during 18 weeks sprouted more rapidly than those stored 8 weeks. A constant “dormancy-like period” (storage duration + sprouting delay) was observed, between 20 and 28 weeks respectively for the more rapid and the slower microtubers. The size of the tubers used for the storage had great influence on further sprouting. The larger they were, the better they sprouted. Light during storage had no effect on the sprouting delay while a temperature of 25 °C permit a quicker sprouting than 18 °C. The medium used to obtain microtubers could also have an effect on sprouting rate. 相似文献
13.
Luc Giasson Charles A. Specht Craig Milgrim Charles P. Novotny Robert C. Ullrich 《Molecular & general genetics : MGG》1989,218(1):72-77
Summary An A mating-type allele (A4) was isolated by walking the chromosome from the closely linked PAB1 gene. A cosmid clone containing the A1 allele isolated from the walk was used as a probe to recover the A1 allele from another cosmid library. Cosmids encoding mating-type activity were identified by transforming Schizophyllum cells and screening for activation of A-regulated development. Putative mating-type transformants were confirmed in mating tests and genetic analyses of progeny. The identity of the specific alleles isolated was demonstrated by showing that their effectiveness in transforming for mating type is limited to recipient strains possessing an A allele different from the one encoded by the cloned sequences. Transforming DNA is active in trans, suggesting that A encodes a diffusible product. Restriction mapping shows that A1 and A4 are coded in the same physical region of the genome, but within a subregion that contains extensive sequence divergence. In addition, Southern analyses show that there is only one copy of A1 or A4 per haploid genome, and that they do not cross-hybridize to one another or to any of the other A alleles. A1 and A4 were subcloned as 2.8 and 1.2 kb fragments, respectively, retaining in transformation all the mating-type activity demonstrated of the original cosmids. 相似文献
14.
The physiological responses to TGF-β stimulation are diverse and vary amongst different cell types and environmental conditions. Even though the principal molecular components of the canonical and the non-canonical TGF-β signaling pathways have been largely identified, the mechanism that underlies the well-established context dependent physiological responses remains a mystery. Understanding how the components of TGF-β signaling function as a system and how this system functions in the context of the global cellular regulatory network requires a more quantitative and systematic approach. Here, we review the recent progress in understanding TGF-β biology using integration of mathematical modeling and quantitative experimental analysis. These studies reveal many interesting dynamics of TGF-β signaling and how cells quantitatively decode variable doses of TGF-β stimulation. 相似文献
15.
β-Glucoside transport by phosphoenolpyruvate-hexose phosphotransferase system in Escherichia coli is inactivated in vivo by thiol reagents. This inactivation is strongly enhanced by the presence of transported substrates. In a system reconstituted from soluble and membrane-bound components, only the particulate component, the membrane-bound enzyme IIbgl appeared as the target of N-ethylmaleimide inactivation. The same feature was found in the case of methyl-α-d-glucoside uptake via enzyme IIglc.It is shown that the sensitizing effect of substrates is specific and not generalized, methyl-α-d-glucoside only sensitizes enzyme IIbglc and only sensitizes enzyme IIbgl towards N-ethylmaleimide inactivation.The inactivation of enzyme IIbgl by thiol reagents is also promoted in vivo by fluoride inhibition of phosphoenolpyruvate synthesis. In toluene-treated bacteria, the presence of phosphoenolpyruvate protects against inactivation by thiol reagents of phosphorylation. Both results suggest that the inactivator resistent form of enzyme IIbgl is an energized form of the enzyme. 相似文献
16.
Jean-Pierre Jost Gundula Pehling Oswald G. Baca 《Biochemical and biophysical research communications》1975,62(4):957-965
Using a combination of radioimmunoprecipitation and SDS-polyacrylamide gel electrophoresis of the immunoprecipitate we studied the rate of synthesis of the heavy chain of β-lipovitellin in the liver of immature chicks. In male and female chicks the base-line synthesis of βL-lipovitellin1 was about 30 molecules per minute and per cell. Four days after a single injection of 40 mg estradiol/kg, as many as 48,000 molecules of βL-lipovitellin were synthesized per minute and per diploid liver cell. The increase in the rate of βL-lipovitellin synthesis could be correlated with an increase in membrane bound mRNA coding for βL-lipovitellin. 相似文献
17.
The interpretation of mass spectra (ms) of molecules containing poly-isotopic elements (e.g. Ge, Se, W, Os, Sn, Te, Zn, Yb)
can be difficult due to the occurrence of fragments resulting from isotopomeric composition. MS-clusters located in the range
lower than or equal to M/2 are very difficult to interpret. In this area many perturbations may be observed. The coincidence
of different fragmentation pathways, the existence of multiply charged ions, background levels, etc. can all contribute to
this problem. The present paper reports the application of multi-isotopomeric analysis methods for low-resolution ms. We present
a solution that may be useful for detection of the symmetrical decomposition of a molecule and for elucidation of cluster
ion genesis. The complex character of the cluster does not perturb determination of the contents of the investigated pattern.
In such cases the dominated component is applied in subsequent computations.
相似文献
Andrzej J. GorączkoEmail: |
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Alexander N. Morozov Cassian D'Cunha Carlos A. Alvarez David C. Chatfield 《Biophysical journal》2011,(4):1066
Molecular dynamics simulations of an explicitly solvated cis-β-methylstyrene/chloroperoxidase-Compound I complex are performed to determine the cause of the high enantiospecificity of epoxidation. From the simulations, a two-dimensional free energy potential is calculated to distinguish binding potential wells from which reaction to 1S2R and 1R2S epoxide products may occur. Convergence of the free energy potential is accelerated with an adaptive biasing potential. Analysis of binding is followed by analysis of 1S2R and 1R2S reaction precursor structures in which the substrate, having left the binding wells, places its reactive double bond in steric proximity to the oxyferryl heme center. Structural analysis of binding and reaction precursor conformations is presented. We find that 1), a distortion of Glu183 is important for CPO-catalyzed epoxidation as was postulated previously based on experimental results; 2), the free energy of binding does not provide significant differentiation between structures leading to the respective epoxide enantiomers; and 3), CPO's enantiospecificity toward cis-β-methylstyrene is likely to be caused by a specific group of residues which form a hydrophobic core surrounding the oxyferryl heme center. 相似文献
20.
Narayanan Sathiya Pandi Muthaiah ManimuthuPalaniswamy Harunipriya Manikandan MurugesanGeorge Virumaandi Asha Suriliyandi Rajendran 《Gene》2014
Actin-binding protein anillin (ANLN) is primarily involved in the cytokinesis and known to be dysregulated in many cancers including gastric cancer (GC). However, the regulation and clinical significance of ANLN in GC are far less clear. In the present study, we aimed to investigate the clinical significance and possible regulators of ANLN in GC. We have identified the Wnt/β-catenin associated regulation of ANLN by analyzing the in vitro perturbed β-catenin mRNA expression profiles. Investigating the gastric tumors from publicly available genome-wide mRNA expression profiles, we have identified the over expression of ANLN in gastric tumors. Association between ANLN expression and clinical characteristics of GC showed elevated expression in intestinal type GC. Performing a single sample prediction method across GC mRNA expression profiles, we have identified the over expression of ANLN in proliferative type gastric tumors compared to the invasive and metabolic type gastric tumors. In silico pathway prediction analysis revealed the association between Wnt/β-catenin signaling and ANLN expression in gastric tumors. Our results highlight that expression of a Wnt/β-catenin responsive gene ANLN in GC is a molecular predictor of intestinal and proliferative type gastric tumors. 相似文献