共查询到20条相似文献,搜索用时 31 毫秒
1.
H Kung M Tainsky H Weissbach 《Biochemical and biophysical research communications》1978,81(3):1000-1010
The regulation of the synthesis of the N-terminal portion of the β-galactosidase molecule (α-peptide) has been investigated using DNA fragments of the lactose operon as template. DNA fragments of about 789 base pairs were isolated after endonuclease (Hin II) digestion of either λplac5, λh80dlacps or λh80dlacUV5 phage DNA or DNA from the recombinant plasmid PMC3. The regulation of the expression of these fragments is similar to that observed for the synthesis of β-galactosidase using total phage or plasmid DNA as template, indicating that the regulatory regions on the fragments are intact and functional. Thus, the synthesis of the α-peptide required an inducer due to the presence of repressor in the S-30 extract used. In addition a dependency on adenosine 3′,5′-cyclic monophosphate (cAMP)1 for α-peptide synthesis was obtained with the fragments isolated from λplac5 and λh80dlacps DNAs, whereas little effect of cAMP was seen with the fragment isolated from λh80dlacUV5 phage DNA or PMC3 plasmid DNA containing a UV5 promotor region. However, a significant difference in the effect of guanosine-3′-diphosphate-5′-diphosphate (ppGpp) was observed. With the total phage DNA as template, ppGpp resulted in a 2–4 fold stimulation whereas with the fragment, or PMC3 plasmid DNA, directed synthesis of the α-peptide no significant stimulation by ppGpp was seen. 相似文献
2.
Exposure of authentic dolichyl α-D-[14C]mannopyranosyl phosphate () or calf pancreas dolichyl [14C]mannopyranosyl phosphate () to ozone at ?70° in pentane followed by treatment with triphenylphosphine gave water-soluble fragments in 65–95% yield. The radioactive products obtained were similar; the major fragment had a mobility on tlc greater than that of mannose but lower than that of citronellyl β-D-mannopyranosyl phosphate. The electrophoretic behavior of the fragments indicated that they possessed intact phosphodiester linkages. α-Mannosidase released [14C]mannose from the fragments of but not from the fragments of ; however, the latter were susceptible to β-mannosidase indicating that the pancreatic mannolipid contains a β-linked mannosyl residue. 相似文献
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Genetic and enzymatic characterization of a conditional lethal mutant of Escherichia coli K12 with a temperature-sensitive DNA ligase 总被引:28,自引:0,他引:28
ts7 an Escherichia coli 15 strain with a thermolabile DNA ligase, has previously been shown to be a temperature-sensitive conditional lethal mutant that is sensitive to methyl methane sulfonate and to ultraviolet irradiation; it also accumulates 10 S DNA fragments to an abnormal extent. When the ligase mutation is transferred to a wild-type E. coli K12 strain, the strain becomes temperature sensitive for growth and displays the same characteristics as ts7. These findings show that a functional DNA ligase is essential for normal DNA replication and repair in E. coli. 相似文献
4.
《Insect Biochemistry》1987,17(1):21-28
Rust-red wild and black mutant strains of the red flour beetle, Tribolium castaneum, were used to investigate temporal patterns of catecholamine and β-alanine content during sclerotization and pigmentation of adult cuticle and to relate these patterns to corresponding changes in cuticle resistance to puncture. Rust-red elytral cuticle sclerotized more rapidly than black cuticle until 6 days after adult eclosion when both became equal in puncture resistance. The cuticular concentrations of (NBAD), β-alanine and 3,4-dihydroxyphenylacetic acid (DOPAC) increased more rapidly in the rust-red strain than in the black strain during the first 7 days following adult eclosion. Conversely, cuticular dopamine increased more rapidly in black than in the red strain. Thus the rust-red pigmentation and rapid sclerotization appear to be related to the availability of β-alanine, and DOPAC. Melanization was prevented and rust-red pigmentation induced by injections of β-alanine or NBAD into newly ecdysed black mutant beetles. Crosses of the two strains generally had intermediate levels of cuticular dopamine and β-alanine, but the NBAD levels were similar to those of the rust-red strain. Dopamine, NBAD and DOPAC levels became similar in both black and rust-red strains about 6 days after adult ecdysis as did resistance to puncture. Therefore, dopamine appears to be directed initially into the melanin pathway in black adults due to a temporary lack of with β-alanine. After the melanization phase, dopamine is metabolized to sclerotization precursors eventually resulting in normal physical properties of the exoskeleton. 相似文献
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Fred E. Cohen Michael J.E. Sternberg William R. taylor 《Journal of molecular biology》1982,156(4):821-862
The packing of α-helices and β-sheets in six proteins (e.g. flavodoxin) has been analysed. The results provide the basis for a computer algorithm to predict the tertiary structure of an protein from its amino acid sequence and actual assignment of secondary structure.The packing of an individual α-helix against a β-sheet generally involves two adjacent ± 4 rows of non-polar residues on the α-helix at the positions i, i + 4, i + 8, i + 1, i + 5, i + 9. The pattern of interacting β-sheet residues results from the twisted nature of the sheet surface and the attendant rotation of the side-chains. At a more detailed level, four of the α-helical residues (i + 1, i + 4, i + 5 and i + 8) form a diamond that surrounds one particular β-sheet residue, generally isoleucine, leucine or valine. In general, the α-helix sits 10 Å above the sheet and lies parallel to the strand direction.The prediction follows a combinational approach. First, a list of possible β-sheet structures (106 to 1014) is constructed by the generation of all β-sheet topologies and β-strand alignments. This list is reduced by constraints on topology and the location of non-polar residues to mediate the sheet/helix packing, and then rank-ordered on the extent of hydrogen bonding. This algorithm was uniformly applied to 16 domains in 13 proteins. For every structure, one member of the reduced list was close to the crystal structure; the root-mean-square deviation between equivalenced Cα atoms averaged 5.6 Å for 100 residues. For the proteins with pure parallel β-sheets, the total number of structures comparable to or better than the native in terms of hydrogen bonds was between 1 and 148. For proteins with mixed β-sheets, the worst case is glyceraldehyde-3-phosphate dehydrogenase, where as many as 3800 structures would have to be sampled. The evolutionary significance of these results as well as the potential use of a combinatorial approach to the protein folding problem are discussed. 相似文献
7.
Effect of aphidicolin on viral and human DNA polymerases. 总被引:9,自引:0,他引:9
DNA polymerases induced by Herpes simplex and Vaccinia viruses are inhibited by aphidicolin and this inhibition is probably the basis of its antiviral activity . Its possible clinical use is however hampered by the concomitant effect on human replicative DNA polymerase α. The inhibition of human α-polymerase is reversible both and and the changes in the rate of incorporation of thymidine into DNA, following treatment with aphidicolin for a generation time, indicate the likely synchronization of the cells due to this agent. DNA polymerase β, which has recently been shown to carry out repair synthesis of damaged nuclear DNA, is not inhibited by aphidicolin either on suggesting that the drug could allow a rapid and simple evaluation of DNA repair synthesis due to DNA polymerase β. 相似文献
8.
Vladimir Divoky Emmanuel Bissé Jerry B. Wilson Li-Hao Gu Heinrich Wieland Irene Heinrichs John F. Prior 《生物化学与生物物理学报:疾病的分子基础》1992,1180(2):173-179
We have analyzed the hemoglobins of a young German patient with β-thalassemia intermedia and of his immediate family and included in these studies an evaluation of possible nucleotide changes in the β-globin through sequencing of amplified DNA. One chromosome of the propositus and one of his father's carried the mutation at codon 126 leading to the synthesis of Hb Dhoburi or α2β2126(H4)Val→Gly; this variant is slightly unstable and is associated with mild thalassemic features. His second chromosome and one of his mother's had the common IVS-I-5 (G→C) mutation that leads to a rather severe β+-thalassemia and the mutation at codon 18, resulting in the replacement of a valine residue by a methionine residue. This newly discovered β-chain variant, named Hb Baden, was present for only 2–3% in both the patient and his mother. This low amount results from a decreased splicing of RNA at the donor splice-site of the first intron that is nearly completely deactivated by the IVS-I-5 (G→C) thalassemic mutation. The chromosome with the codon 18 () and the IVS-I-5 (G→C) mutations has thus far been found only in this German family; analysis of 51 chromosomes from patients with the IVS-I-5 (G→C) mutation living in different countries failed to detect the codon 18 () change. 相似文献
9.
B I Sinzinis G B Smirnov A A Saenko 《Biochemical and biophysical research communications》1973,53(1):309-316
The effect of ultraviolet irradiation (UV) has been studied in mutator UV-sensitive mutant , its derivative and wild-type strain. The mutant is about 5 times more UV-sensitive than the + isogenic strain, but 3 times less sensitive than the single mutant. Cells of the mutant are unable to rejoin the fragments of parental DNA formed after UV as a result of incision. The double mutant as well as the single mutant irradiated with UV is unable to introduce breaks into parental DNA. The extent of postreplication repair is essentially normal in the cells. There is no significant difference between the and cells in the rate and extent of UV-induced DNA degradation. 相似文献
10.
Hans R. Kricheldorf Detlef Müller 《International journal of biological macromolecules》1983,5(3):171-178
13C n.m.r. CP/MAS spectra (50.3 and 75.4 MHz) of solid poly(l-lleucines) and poly(d-norvalines) measured with suitable acquisition parameters allow quantification of the composition of the secondary structure. The optimum acquisition parameters were found by systematic variation of the contact time by means of samples containing 5?0% α-helix structure. The polypeptides were prepared by primary or tertiary amine-initiated polymerizations of the corresponding amino acid NCAs and the average degrees of polymerization () were determined by 1H n.m.r. endgroup analysis. The mole fraction of α-helices increases with increasing ; it depends on the nature of the solvent and to a lesser degree on the polymerization temperature. When prepared under identical conditions, poly(d-norvaline) samples contain more β-sheet structure than poly(l-leucine. Reprecipitation increases the α-helix content, demonstrating that a part of the original β-sheet structure is thermodynamically unstable. The presence of oligomers of ?10 is mainly responsible for the thermodynamically stable part of the β-sheet structure. The chain growth mechanism is discussed. 相似文献
11.
The replication defective transducing phage λp3 carries a portion of the operon in the 2 region of the lambda phage. This operon segment contains the promoter, the operator, and the β-galactosidase gene, but does not contain the repressor gene. The gene can be expressed from both the inserted promoter and the phage promoter. When strain 594 (?, +) or JC6256 (Δ) is infected by λp3 in the absence of additional cyclic AMP, β-galactosidase synthesis is shown to be expressed from the phage promoter. When 594 (λ+) or JC6256 (λ+) is infected by λp3 in the presence of additional cyclic AMP and IPTG, β-galactosidase synthesis is shown to be expressed from the inserted promoter.The ability to separate the phage promoter from the inserted promoter for β-galactosidase expression will simplify the interpretation whenever λp5 is used. 相似文献
12.
The isolated myenteric plexus-longitudinal muscle of the guinea-pig ilem (GPI) was used as testsystem to study the influence of chronic morphine treatment on the levels of enkephalins, β-endorphin and some of its fragments. The peptides were assayed by means of a combination of high pressure liquid chromatography and radioimmunoassays. It was found that the levels of methionine- and leucine-enkephalin and β-endorphin were not altered by chronic morphine treatment of guinea-pigs nor in GPI exposed to morphine . However, the levels of some β-endorphin fragments i.c. γ-endorphin and des-tyrosine-γ-endorphin were elevated after morphine treatment and respectively. It is suggested that β-endorphin and its fragments are involved in homeostatic processes during development of opiate tolerance. 相似文献
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15.
Toshiro Matsunaga Akira Okubo Motohiro Fukami Sunao Yamazaki Shozo Toda 《Biochemical and biophysical research communications》1981,102(1):524-530
Polysaccharides, which come into resonances in the 13C NMR spectrum of intact mycelium and give anomeric carbon signals at 107.5 and 108.3 ppm, are associated with the cell wall. By 13C NMR and gas liquid chromatography analysis, it is shown that the polysaccharides are two types of β-galactofuranosyl residues, one of which has (1→2)-β-galactofuranosyl linkages. Both β-galactofuranosyl residues, which are minor cell wall components, experience rapid internal motion in the cell wall. 相似文献
16.
D. Gersanovski P. Colson C. Houssier E. Fredericq 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1985,824(4):313-323
At low ionic strength, Tb3+ binding strongly alters the secondary structure of DNA. Circular dichroism and electro-optical techniques are more sensitive than fluorescence to study these alterations in double-stranded DNA, at low Tb3+/DNA phosphate () ratios. Both techniques yield the following conclusion: as is increased, native and sonicated DNA undergo a transition from the B- to ψ-form, the latter being a compact structure characteristic of aggregated DNA. Our study of alkylated DNA establishes that the accessibility of N-7 guanine to Tb3+ is clearly required for structural alterations in an aggregated state to occur. The chelation of the phosphate group and of the N-7 guanine by Tb3+ simultaneously alters the geometry of the sugar-phosphate backbone and the stacking interaction between the bases in double-stranded DNA. 相似文献
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The chain elongation of rat liver DNA following partial hepatectomy was studied using alkaline sucrose gradients. DNA made in 5 min was less than 4 × 107 daltons and that made in 30 min was heterodisperse and by 4 hr 75% of the DNA became larger than 1 × 109 daltons. Administration of 1-β-D-arabinofuranosyl cytosine (ara-C) 5 min after thymidine-3H injection inhibited the chain elongation, whereas if given 30 minutes after thymidine-3H pulse did not inhibit the chain elongation. Thus the chain elongation of rat liver DNA consists of at least two steps 1) a step sensitive to ara-C involving nucleotides addition and 2) the other insensitive to ara-C and probably involving ligation of polynucleotide chains. 相似文献
19.
Synthesis of simian virus 40 DNA in isolated nuclei 总被引:1,自引:0,他引:1
P K Qasba 《Biochemical and biophysical research communications》1974,60(4):1338-1344
The presence or absence of calcium ions during the isolation of nuclei from SV40-infected African green monkey kidney cells significantly affects the size of SV40 DNA synthesized . When Ca++ is present during the nuclear isolation procedure, the 3–7S fragments of SV40 DNA synthesized mature into long chains; in the absence of Ca++ they do not. 相似文献
20.
The β-lactamase (penicillinase) from Escherichia coli W3310 has been crystallized from 25% saturated ammonium sulfate solution at pH 6.9. An X-ray examination of the monoclinic crystals shows the space group is C2, with unit cell dimensions , , and β = 98.6°. With Z = 4 and the molecular weight = 22,000 (Melling &; Scott, 1972), the Å3/dalton ratio is 2.98. The crystals are suitable for structure analysis to at least 2.4 Å resolution. 相似文献