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PubMed1997

Information transfer in multienzyme complexes--2. The role of Arg64 of Chlamydomonas reinhardtii phosphoribulokinase in the information transfer between glyceraldehyde-3-phosphate dehydrogenase and phosphoribulokinase.

A mutant phosphoribulokinase has been isolated from the 12-2B mutant of Chlamydomonas reinhardtii. In this mutant, Arg64 has been replaced by Cys. The enzyme, which may exist in the dimeric and tetrameric states, is almost devoid of activity. Neither of these enzymes is able to form a complex with glyceraldehyde-3-phosphate dehydrogenase. The phosphoribulokinase gene has been expressed in Escherichia coli. The resulting recombinant protein, after isolation and purification, is apparently identical to the native enzyme extracted from the chloroplast. Three mutants have been generated by site directed mutagenesis. Arg64 has been replaced by Ala, Lys or Glu. With the exception of the latter, the two other mutants, [A64]phosphoribulokinase and [K64]phosphoribulokinase, are active when they are reduced, and nearly totally inactive in their oxidized state. Their activity, however, is decreased relative to that of the native, or to that of the wild-type recombinant phosphoribulokinase. Both the catalytic constant and the apparent affinity of ribulose 5-phosphate are decreased relative to the corresponding values obtained for the wild-type, the native or the recombinant enzyme. Whereas the [A64]phosphoribulokinase is unable to form a complex with glyceraldehyde-3-phosphate dehydrogenase, [K64]phosphoribulokinase does, but the stability of the resulting complex is much decreased relative to that of the wild-type complex. The oxidized mutant [K64]phosphoribulokinase becomes active in the presence of glyceraldehyde-3-phosphate dehydrogenase but this activity is smaller than that of the corresponding wild-type enzyme. Taken together, these results show that Arg64 plays a major role in the association of the two enzymes and in the information transfer that takes place between glyceraldehyde-3-phosphate dehydrogenase and phosphoribulokinase. As this residue also appears to be important for catalytic activity, it may be tempting to consider that it stabilizes a conformation that is required for both the catalytic activity and the formation of the bienzyme complex.

Animals↗

PubMed1972

Regulation of histidyl-transfer ribonucleic acid synthetase formation in a histidyl-transfer ribonucleic acid synthetase mutant of Salmonella typhimurium.

Control of formation of the histidyl-transfer ribonucleic acid (tRNA) synthetase with an increased K(m) for histidine was studied in a hisS mutant of Salmonella typhimurium. Histidine restriction of both the hisS and hisS(+) strains resulted in a derepression of synthesis of histidyl-tRNA synthetase. When grown in a concentration less than the K(m) (100 mug/ml) of l-histidine, the hisS mutant maintained a higher level of histidyl-tRNA synthetase than the hisS(+) strain. Addition of excess amounts of l-histidine to the growth medium of the hisS mutant culture grown with 100 mug of l-histidine per ml resulted in a repression of histidyl-tRNA synthetase formation to equal that of the hisS(+) strain grown in 100 mug of l-histidine per ml. These data confirm previous findings that histidine tRNA is involved in the repression of synthesis of histidyl-tRNA synthetase.

Amino Acyl-tRNA Synthetases↗

PubMed1981

Number and size of human X chromosome fragments transferred to mouse cells by chromosome-mediated gene transfer.

Labeled probes of unique-sequence human X chromosomal deoxyribonucleic acid, prepared by two different procedures, were used to measure the amount of human X chromosomal deoxyribonucleic acid in 12 mouse cell lines expressing human hypoxanthine phosphoribosyltransferase after chromosome-mediated gene transfer. The amount of X chromosomal deoxyribonucleic acid detected by this procedure ranged from undetectable levels in the three stable transformants and some unstable transformants examined to about 20% of the human X chromosome in two unstable transformants. Reassociation kinetics of the X chromosomal probe with deoxyribonucleic acid from the two unstable transformants containing 15 to 20% of the human X chromosome indicate that a single copy of these sequences is present. In one of these lines, the X chromosomal sequences exist as multiple fragments which were not concordantly segregated when the cells were selected for loss of hprt.

Animals↗

PubMed1982

Transfer of nonselectable genes into mouse teratocarcinoma cells and transcription of the transferred human beta-globin gene.

Teratocarcinoma (TCC) stem cells can function as vehicles for the introduction of specific recombinant genes into mice. Because most genes do not code for a selectable marker, we investigated the transformation efficiency of vectors with a linked selectable gene. In one series, TCC cells first selected for thymidine kinase deficiency were treated with DNA from the plasmid vector PtkH beta 1 containing the human genomic beta-globin gene and the thymidine kinase gene of herpes simplex virus. A high transformation frequency was obtained after selection in hypoxanthine-aminopterin-thymidine medium. Hybridization tests revealed that the majority of transformants had intact copies of the human gene among three to six total copies per cell. These were associated with cellular DNA sequences as judged from the presence of additional new restriction fragments and from stability of the sequences in tumors produced by injecting the cells subcutaneously. Total polyadenylate-containing RNA from cell cultures of two out of four transformants examined showed hybridization to the human gene probe: one RNA species resembled mature human beta-globin mRNA transcripts; the others were of larger size. In differentiating tumors, various tissues, including hematopoietic cells of TCC provenance could be found. In a second model set of experiments, wild-type TCC cells were used to test a dominant-selection scheme with pSV-gpt vectors. Numerous transformants were isolated, and their transfected DNA was apparently stably integrated. Thus, any gene of choice can be transferred into TCC stem cells even without mutagenesis of the cells, and selected cell clones can be characterized. Cells of interest may then be introduced into early embryos to produce new mouse strains with predetermined genetic changes.

Animals↗

PubMed1976

Transferable and non-transferable drug resistance in enteric bacteria from hospital and from general practice.

Drug resistance to 8 different antibiotics in Enterobacteriaceae isolated from different hospitals and two groups of general practitioners was studied. Escherichia coli dominated among the 632 strains investigated. Drug resistance was found in 62% of the 512 hospital strains and in 38% of the 120 strains from general practice. Multiple resistance was common especially in strains from hospital. R factors was found in 23% of the 317 drug-resistant strains from hospital and in 11% of the 46 drug-resistant strains from general practice. Resistance to streptomycin, sulphonamide and tetracycline either alone or in combinations were the most common traits transferred.

Anti-Bacterial Agents↗

PubMed1999

Novel U-Shaped Systems Containing an Imide-Functionalized Cleft for the Study of Solvent-Mediated Electron Transfer and Energy Transfer: Synthesis and Binding Studies.

A solution to the vexing problem of investigating solvent-mediated electron transfer under conditions of frozen solvent motion may be at hand with the synthesis of novel U-shaped systems such as 1 (R=CO(2)Me) and 2 (R=CH(2)OMe), in which the imide-functionalized cleft provides the point of attachment of the "solvent" molecule, either covalently or by hydrogen bonding.

Journal Article↗

PubMed2001

Scan-rescan variation of measures derived from brain magnetization transfer ratio histograms obtained in healthy volunteers by use of a semi-interleaved magnetization transfer sequence.

SUMMARY: A novel semiinterleaved gradient-echo (GE) sequence for quantitative measurement of magnetization transfer ratio (MTR) is described. With this sequence, several lines of k-space are collected for the non-MT image then several lines are collected for the MT image, thus building up the entire k-space in distinct acquisition blocks, with a good trade-off between motion-induced misregistration and degree of MT effect. The scan-rescan coefficients of variation for several MTR histogram-derived measures from 10 healthy volunteers scanned serially with this semiinterleaved sequence proved to be lower than those achieved using a conventional GE sequence. This sequence may be useful in a clinical environment to measure MTR changes over time more reliably than when acquiring the non-MT and MT images sequentially, which inevitably are affected by patient motion.

Adult↗

PubMed1992

DNA cassettes containing the origin of transfer (oriT) of two broad-host-range transfer systems.

Plasmid constructs are described that carry retrievable DNA cassettes containing the origin of transfer region (oriT) from two broad-host-range plasmids. Restriction of these high copy number plasmids with any one of a variety of enzymes yields a linear DNA fragment of convenient size containing the oriT region of either pCUI or RK2. This DNA can be ligated into any vector or recombinant plasmid containing a compatible enzyme site and can be easily identified by size on an agarose gel. Any plasmid can therefore be mobilized using a number of helper strains or conjugative plasmids derived from the parental plasmids. In addition, the cassettes can be used for a variety of genetic manipulations including "selectable" linker mutagenesis.

Cloning, Molecular↗

PubMed1978

Transfer of immunity by transfer of bone marrow cells: a requirement for T lymphocytes and sensitivity to cyclophosphamide.

Thymectomized, lethally irradiated mice reconstituted with bone marrow cells (TIR mice) from normal donors succumbed after i.p. challenge with xenogeneic (rat) Yoshida ascites sarcoma (YAS) given 1 month after irradiation and reconstitution. YAS rejection and production of YAS-antibodies was induced in TIR mice by a single i.v. injection of normal syngeneic spleen cells given 1 day after the tumor. Purified splenic T lymphocytes also induced YAS rejection in TIR mice, but splenic B lymphocytes did not affect progressive tumor growth. Tumor was also rejected in TIR mice that had been reconstituted with bone marrow cells from YAS-immune donors. The sera of these TIR mice did not contain tumor antibodies between reconstitution and YAS challenge, but a high YAS-antibody titer was present after YAS challenge and rejection. Immunofluorescence did not reveal any dramatic differences in the spleen and bone marrow content of T and B lymphocytes of TIR mice reconstituted with cells from normal donors and those reconstituted with cells from the YAS-immunized donors. Transfer of YAS-resistance was abolished when the bone marrow cells from immunized donors were treated with Thy 1.2 antiserum and complement, or when bone marrow donors were injected with cyclophosphamide 1 day after immunization. Cyclophosphamide was also shown to induce strong and specific suppression of YAS-antibody production in normal mice.

Animals↗

PubMed1971

Transfer amyloidosis. I. Studies on the transfer of various lymphoid cells from amyloidotic mice to syngeneic nonamyloidotic recipients. II. Induction of amyloidosis in mice with spleen, thymus and lymph node tissue from casein-sensitized syngeneic donors.

Lymphoid cells from various lymphoid organs were transferred from amyloidotic mice to normal syngeneic recipients. The recipients were treated with nitrogen mustard. Only the recipients of spleen cells developed amyloidosis. Furthermore, slices of spleen, thymus and lymph node from casein-sensitized mice were transplanted to kidneys of normal syngeneic mice. The recipients were treated with ten casein injections, and they all developed amyloidosis. The results from both experiments indicate that amyloid is formed by macrophages due to a stimulation of these cells with both antigen and an amyloid-inducing factor released from the pyroninophilic lymphoid cells.

Amyloidosis↗

PubMed1981

[Conjugation transfer of chromosome markers in an Erwinia chrysanthemi bacterial system. I. Construction of a strain capable of transferring the chromosome during conjugation].

The donor strain Erwinia chrysanthemi VY1-10, capable of transferring chromosomal markers at a high frequency (4,7.10(-5)-1,8.10(-3) in crosses with the isogenic polyauxotrophic recipient strain E. chrysanthemi VY7 lac, thr1, leu1, pro1, his2, str-r, was obtained from the strain E. chrysanthemi ENA49 Flac+ (VY1) after growth at 28 degrees on the medium containing acridine orange. Furthermore, the cells of the donor obtained are characterized by stable inheritance of lac+ character.

Chromosomes, Bacterial↗

PubMed1995

[Maternal transfer and neonatal transfer].

Regionalisation of perinatal health care has not been organised in France. This concept has proposed to reduce mortality and morbidity of newborns of less than 33 weeks or less than 1,500 g at birth by a transfer of the mother before birth to a perinatal center with a neonatal intensive care unit. The available information in France shows that only 14% of those infants will be born in a level 3 centres. In Seine-Saint-Denis district available information shows that the adds ratio for per partum and neonatal death for newborns of 28-36 gestation duration is of 5.27 when a level 1 maternity is compared to a level 3.

Female↗

PubMed1979