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101.
Methane monooxygenase mutants of Methylosinus trichosporium constructed by marker-exchange mutagenesis 总被引:1,自引:0,他引:1
Abstract Methylosinus trichosporium OB3b synthesizes a soluble cytoplasmic methane monooxygenase when grown in copper-depleted medium and a membrane-bound particulate methane monooxygenase under copper-replete conditions. The genes encoding the hydroxylase component of soluble methane monooxygenase, carried on a plasmid in Escherichia coli , were insertionally inactivated using a kanamycin cassette and transferred back into M. trichosporium by conjugation. Marker-exchange mutagenesis, via a double homologous recombination event, yielded a soluble methane monooxygenase-negative mutant which grew only on methane using the particulate methane monooxygenase during copper-replete growth conditions, thus proving that the two methane oxidation systems in this methanotroph are genetically distinct. 相似文献
102.
K. Kitamura C. S. Davies N. C. Nielsen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,68(3):253-257
Summary A cultivar lacking the glycinin subunit A5A4B3 (Raiden) was crossed with one lacking the -subunit of -conglycinin (Keburi). Analysis of F2 and F3 progeny indicated that the missing bands of the A5A4B3 and the -subunit were each controlled by a recessive allele of two independently segregating genes. Gene symbols Gy
4/gy
4 and Cgy
1/cgy
1 were proposed for the genes which confer the presence or absence of the glycinin and conglycinin subunits, respectively.Cooperative research of USDA-ARS and the Indiana Agric. Exp. Stn., Purdue Univ., West Lafayette, IN 47907, USA. Indiana Agric. Exp. Stn. Journal Article 9675. Financial support from the American Soybean Association Research Foundation is gratefully acknowledged 相似文献
103.
Heinz Rotering Waltraud Fiedler Wolfgang Rollinger Volkmar Braun 《FEMS microbiology letters》1984,22(1):61-68
Abstract A mutant screening procedure is described which allows the identification of mutants carrying lesions in lipoprotein, membrane-derived oligosac-charides (MDO), and other compounds of the E. coli cell envelope containing glycerol derived from phospholipid metabolism. Two mutants lacking glycerol in MDO and one mutant devoid of lipoprotein demonstrate the usefulness of the procedure. 相似文献
104.
The growth zone of the sporangiophore of a piloboloid mutant,pil, ofPhycomyces expands radially at an increased rate until the growth zone becomes nearly spherical, in sharp contrast to that of the wild-type sporangiophore which exhibits longitudinal elongation only and is conical. The rotation of thepil sporangiophore reverses its direction from clockwise (CW) to counterclockwise (CCW) during the period of increased radial expansion, and the CCW rotation continues as long as does the radial expansion. The direction of rotation and the time of reversal are correlated with the relative rates of cell-wall expansion in the longitudinal and transverse directions. The CCW rotation of the sporangiophore of this mutant can be explained by the behavior of the microfibrils, as previously proposed to explain the rotation of the wild-type sporangiophore.Abbreviations CW
clockwise
- CCW
counterclockwise — both as viewed from above 相似文献
105.
The regulation of the development of nitrate reductase (NR) activity in Chlamydomonas reinhardii has been compared in a wild-type strain and in a mutant (nit-A) which possesses a modified nitrate reductase enzyme that is non-functional in vivo. The modified enzyme cannot use NAD(P)H as an electron donor for nitrate reduction and it differs from wild-type enzyme in that NR activity is not inactivated in vitro by incubation with NAD(P)H and small quantities of cyanide; it is inactivated when reduced benzyl viologen or flavin mononucleotide is present. After short periods of nitrogen starvation mutant organisms contain much higher levels of terminal-NR activity than do similarly treated wild-type ones. Despite the inability of the mutant to utilize nitrate, no nitrate or nitrite was found in nitrogen-starved cultures; it is therefore concluded that the appearance of NR activity is not a consequence of nitrification. After prolonged nitrogen starvation (22 h) the NR level in the mutant is low. It increases rapidly if nitrate is then added and this increase in activity does not occur in the presence of ammonium, tungstate or cycloheximide. Disappearance of preformed NR activity is stimulated by addition of tungstate and even more by addition of ammonium. The results are interpreted as evidence for a continuous turnover of NR in cells of the mutant with ammonium both stimulating NR breakdown and stopping NR synthesis. Nitrate protects the enzyme from breakdown. Reversible inactivation of NR activity is thought to play an insignificant rôle in the mutant.Abbreviations NR
nitrate reductase
- BV
benzyl viologen 相似文献
106.
The incorporation of3H-thymidine into DNA in the brains of the 17-day and 20-day old rat fetuses was significantly reduced by maternal zinc restriction
during pregnancy. The activity of the enzyme thymidine kinase (EC 2.7.1.21) was similarly reduced in the zine-deprived fetal
brains on days 14 and 20 of gestation, but not on day 17. Fetal brain alkaline phosphatase (EC 3.1.3.1) was significantly
depressed by maternal zinc deprivation on days 17 and 20 of pregnancy.
The data suggest an association between thymidine kinase and the reduced incorporation of3H-thymidine into DNA in the brains of 20-day old fetuses but not in animals on day 17. Alkaline phosphatase was however depressed
at this stage.
The suggestion is made that because of the complexity of brain development, future biochemical studies in this area should
concern specific structures in the brain at particular critical stages during neurogenesis. 相似文献
107.
P. Pasquali L. Landi L. Cabrini G. Lenaz 《Journal of bioenergetics and biomembranes》1981,13(3-4):141-148
Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms ofK
M, although a decrease ofV
max is sometimes observed. Experiments with submitochondrial particles from a UQ-deficient mutant ofS. cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III. 相似文献
108.
S. Rambhav 《Journal of biosciences》1981,3(3):221-226
The single side chain amino group of the D-ornithine residue in bacitracin seems to be important for the antibacterial activity
of the molecule, since, acetylation, formylation, carbamylation and deamination of the antibiotic caused 90–92% loss of antibacterial
activity. In contrast, nearly 80–91% of the antibacterial activity of the parent antibiotic was retained after the esterification,
amide formation and acid-chloride formation of the α—and Y -carboxyl groups of D-asparagine and D-glutamic acid residues of
the antibiotic, respectively. 相似文献
109.
Summary Inverted pyramidal neurons are very abundant in the cerebral cortex of the adult reeler mutant mouse. Two types of inverted pyramid are found in rapid Golgi impregnations. In the first type the axon starts from the base of the cell body and bends towards the white matter. In the second type, which is more common, the axon emerges from the apical dendritic tree and descends directly towards the white matter.Despite its abnormal topography, the site of origin of the axon in pyramids of the second type displays a normal differentiation, when analysed with the electron microscopic Golgi technique, suggesting that the ectopic initial axon segment is able to fulfil its normal functions. 相似文献
110.
Developmental controls of morphological mutants of Phaseolus vulgaris L. conditioned by two independent loci, DL1 and DL2, were examined through grafting experiments and hydroponic studies. Phenotypes of mutant classes were duplicated by unions of scions and stocks derived from different genotypes. Results indicate that DL1 and DL2 regulate a root and shoot factor respectively, contributing to the mutant types. The allelic dosages of DL1 in the root and DL2 in the shoot rather than the genotype of the whole plant per se determine the severity of the mutant expression. Plants heterozygous for both loci with a temperature-sensitive expression of the mutant phenotype were used to determine physiological components involved. The primary abnormal developmental event associated with the appearance of mutant phenotypes, the restricted root growth at high temperature, could be overcome by the addition of cytokinin in hydroponic solution. These observations suggest that DL1 and DL2 may be related to the regulation of hormonal function or metabolism. 相似文献