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31.
Flora Sánchez Angeles Touriño Susana Traseira Agustín Pérez-Aranda Víctor Rubio Miguel A. Peñalva 《Molecular & general genetics : MGG》1986,205(2):248-252
Summary We cloned the Penicillium chrysogenum trpC gene from a genomic library by complementation of an Escherichia coli trpC mutant lacking phosphoribosylanthranilate isomerase activity. The gene ecodes a 2.7 kb poly(A)+ RNA. We localized the gene by sequence analysis in a 2.9 kb DNA insert found in the smallest plasmid selected from the library. Sequence data strongly suggest that the organization of the gene is similar to that described in other Ascomycetes. We found that a DNA fragment which codes only for the carboxy-terminal protion of the polypeptide is sufficient for complementation of the E. coli trpC9830 mutation. 相似文献
32.
Dr. Manuel Megias Miguel A. Caviedes Francisco Rodriguez-Quiñones Antonio J. Palomares Francisco Ruiz-Berraquero 《Current microbiology》1985,12(6):325-328
Rhizobium trifolii was highly resistant to the lethal effect ofN-methyl-N-nitro-N-nitrosoguanidine (MNNG), but it was sensitive to the mutagenic action of this chemical. A concentration of 500g/ml yields a survival of between 1% and 10%, which allows us to obtain a higher number of mutants than lower concentrations that yield higher survival rates. Lethal damage produced by nitrosoguanidine was repaired, and repair is inhibited by acriflavine. 相似文献
33.
Luis M. Vázquez de Miguel José A. Serrano Blázquez Fernando J. García Barros Manuel Gómez Guillén 《Carbohydrate research》1984,126(1):81-90
Ethyl 2-amino-4,6-O-benzylidene-2-deoxy-d-gluconate adds to acetylenic esters to give sugar enaminones. The following acetylene derivatives have been employed: methyl propiolate, ethyl phenylpropiolate, and dimethyl acetylenedicarboxylate (6). With compound 6, the reaction leads to a mixture of the expected enaminone and the isomeric oxazolidine derivative. The structures and configurations of the new compounds were studied by spectroscopic and chemical methods. 相似文献
34.
Microbial metabolism of chlorosalicylates: effect of prolonged subcultivation on constructed strains
Miguel Angel Rubio Karl-Heinrich Engesser Hans-Joachim Knackmuss 《Archives of microbiology》1986,145(2):123-125
The hybrid strain Pseudomonas sp. WR4016 was subcultivated with increasing concentrations of 5-chlorosalicylate (510 mM) as sole carbon source over a period of 9 months. At intervals of approximately 3 months derivative strains WR4017, WR4018 and WR4019 were isolated which exhibited higher growth rates and increased substrate tolerance. Comparative analysis of the turnover rates of the key enzymes in chlorosalicylate degradation showed that the adaptation process did not result from structural modifications of these proteins. Instead, balanced over-production of the salicylate hydroxylase and catechol 1,2-dioxygenase prevented the accumulation of toxic chlorocatechols and accounted for the reduction of the doubling times with 4- or 5-chlorosalicylate. A comparative analysis of a genetically engineered chlorosalicylate degrader PL300-1 showed similar regulatory patterns as the most advanced isolate WR4019 from the adaptation series. 相似文献
35.
Purification of the colicin I receptor 总被引:3,自引:0,他引:3
The colicin I outer membrane receptor was solubilized from the cell envelope of Escherichia coli K12 by extraction with Triton X-100 and purified to homogeneity by a combination of ion exchange and gel filtration chromatography as well as isoelectric focusing. The receptor was isolated as a single polypeptide and retained capacity to form a complex with pure colicin. The apparent molecular weight of the receptor as determined by polyacrylamide gel electrophoresis in sodium dodecy sulfate was 74,000 or 54,000 depending on whether the preparation was boiled or not in sodium dodecyl sulfate, respectively, prior to electrophoresis. Isoelectric focusing of the receptor in the presence of Triton X-100 revealed that the protein was slightly acidic (pI 4.75). 相似文献
36.
37.
The rate of photosynthetic nitrate utilization in Anacystis nidulans is strongly influenced by the availability of carbon dioxide. This dependence can be relieved by inhibiting the metabolism of the ammonium derived from nitrate reduction. Nitrate uptake seems to be modulated through a sensitive regulatory system integrating the photosynthetic metabolism of carbon and nitrogen, with CO2 fixation products antagonizing the inhibitory effect of ammonium derivatives. 相似文献
38.
39.
Jorge Briozzo Lidia Núncez Jorge Chirife León Herszage Miguel D'aquino 《Journal of applied microbiology》1989,66(1):69-75
Essential oil of clove, dispersed (0.4%v/v) in a concentrated sugar solution, had a marked germicidal effect against various bacteria and Candida albicans. Staphyloccus aureus (five strains), Klebsiella pneumoniae, Pseudomonas aeruginosa, Clostridium perfringens , and Escherichia coli inoculated at a level of 107 cfu/ml, and C. albicans (inoculum 4.0×105 cfu/ml) were killed (< 99.999%) after 2–7 min in a laboratory broth supplemented with 63% (v/w) of sugar, and containing 0.4% (v/w) of essential oil of clove. Added organic matter (i.e. human or bovine serum) did not impair its antimicrobial activity.
Sugar was not necessary for the antimicrobial activity of clove oil, but the concentrated sugar solution provided a good vehicle for obtaining an oil dispersion that is relatively stable for certain practical applications. 相似文献
Sugar was not necessary for the antimicrobial activity of clove oil, but the concentrated sugar solution provided a good vehicle for obtaining an oil dispersion that is relatively stable for certain practical applications. 相似文献
40.
A peptide (PCB1) corresponding to the proregion of the rat cysteine protease cathepsin B was synthesized and its ability to inhibit cathepsin B activity investigated. PCB1 was found to be a potent inhibitor of mature cathepsin B at pH 6.0, yielding a Ki = 0.4 nM. This inhibition obeyed slow-binding kinetics and occurred as a one-step process with a k1 = 5.2 x 10(5) M-1 s-1 and a k2 = 2.2 x 10(-4) s-1. On dropping from pH 6.0 to 4.7, Ki increased markedly, and whereas k1 remained essentially unchanged, k2 increased to 4.5 x 10(-3) s-1. Thus, the increase in Ki at lower pH is due primarily to an increased dissociation rate for the cathepsin B/PCB1 complex. At pH 4.0, the inhibition was 160-fold weaker (Ki = 64 nM) than at pH 6.0, and the propeptide appeared to behave as a classical competitive inhibitor rather than a slow-binding inhibitor. Incubation of cathepsin B with a 10-fold excess of PCB1 overnight at pH 4.0 resulted in extensive cleavage of the propetide whereas no cleavage occurred at pH 6.0, consistent with the formation of a tight complex between cathepsin B and PCB1 at the higher pH. The synthetic propeptide of cathepsin B was found to be a much weaker inhibitor of papain, a structurally similar cysteine protease, and no pH dependence was observed. Inhibition constants of 2.8 and 5.6 microM were obtained for papain inhibition by PCB1 at pH 4.0 and 6.0, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献