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301.
Patterns of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) variation
were studied in 378 populations of oak trees sampled throughout the
southern half of France. Six cpDNA haplotypes detected in a previous
European survey and three new cpDNA haplotypes were found in this region.
Two mitochondrial polymorphisms detected earlier by restriction analysis of
PCR-amplified fragments alone, or in combination with single-strand
conformation polymorphism (SSCP), were compared with the cpDNA data.
Sequencing revealed the nature of the two mitochondrial mutations: a
single-base substitution and a 4-bp inversion associated with a 22-bp
hairpin secondary structure. The single-base substitution was then analyzed
by allele-specific amplification. Results for the two cytoplasmic genomes
were combined, which allowed the identification of 12 cpDNA-mtDNA
haplotypes. The 4-bp mtDNA inversion has appeared independently in
different cpDNA lineages. Given the peculiar nature of this mtDNA mutation,
we suggest that intramolecular recombination leading to repeated inversions
of the 4-bp sequence (rather than paternal leakage of one of the two
genomes) is responsible for this pattern. Furthermore, the geographic
locations of the unusual cpDNA-mtDNA associations (due to the inversion)
usually do not match the zones of contact between divergent haplotypes. In
addition, in southern France, the groupings of populations based on the
mtDNA substitution were strictly congruent with those based on cpDNA.
Because many populations that are polymorphic for both cpDNA and mtDNA have
remained in contact since postglacial recolonization in this area without
producing any new combination of cytoplasms involving the mitochondrial
substitution, we conclude that paternal leakage is not a significant factor
at this timescale. Such results confirm and expand our earlier conclusions
based on controlled crosses.
相似文献
302.
Cytosolic isocitrate dehydrogenase in humans, mice, and voles and phylogenetic analysis of the enzyme family 总被引:3,自引:0,他引:3
Nekrutenko A; Hillis DM; Patton JC; Bradley RD; Baker RJ 《Molecular biology and evolution》1998,15(12):1674-1684
In this study, we report cDNA sequences of the cytosolic NADP-dependent
isocitrate dehydrogenase for humans, mice, and two species of voles
(Microtus mexicanus and Microtus ochrogaster). Inferred amino acid
sequences from these taxa display a high level of amino acid sequence
conservation, comparable to that of myosin beta heavy chain, and share
known structural features. A Caenorhabditis elegans enzyme that was
previously identified as a protein similar to isocitrate dehydrogenase is
most likely the NADP-dependent cytosolic isocitrate dehydrogenase enzyme
equivalent, based on amino acid similarity to mammalian enzymes and
phylogenetic analysis. We also suggest that NADP-dependent isocitrate
dehydrogenases characterized from alfalfa, soybean, and eucalyptus are most
likely cytosolic enzymes. The phylogenetic tree of various isocitrate
dehydrogenases from eukaryotic sources revealed that independent gene
duplications may have given rise to the cytosolic and mitochondrial forms
of NADP-dependent isocitrate dehydrogenase in animals and fungi. There
appears to be no statistical support for a hypothesis that the
mitochondrial and cytosolic forms of the enzyme are orthologous in these
groups. A possible scenario of the evolution of NADP-dependent isocitrate
dehydrogenases is proposed.
相似文献
303.
J J Quinlan J T Nickels W I Wu Y P Lin J R Broach G M Carman 《The Journal of biological chemistry》1992,267(25):18013-18020
Evidence is presented that demonstrated that the 45- and 104-kDa forms of phosphatidate phosphatase from Saccharomyces cerevisiae (Morlock, K. R., McLaughlin, J. J., Lin, Y.-P., and Carman, G. M. (1991) J. Biol. Chem. 266, 3586-3593) were regulated differentially by phosphorylation. Purified 45-kDa phosphatidate phosphatase was phosphorylated by cAMP-dependent protein kinase whereas purified 104-kDa phosphatidate phosphatase was not phosphorylated. cAMP-dependent protein kinase catalyzed the phosphorylation of pure 45-kDa phosphatidate phosphatase at a serine residue which resulted in a stimulation (2.4-fold) of phosphatidate phosphatase activity. Alkaline phosphatase catalyzed the dephosphorylation of pure 45-kDa phosphatidate phosphatase which resulted in an inhibition (1.3-fold) of phosphatidate phosphatase activity. Results of studies using mutants (bcy1 and cyr1) defective in cAMP-dependent protein kinase activity corroborated the results of the phosphorylation studies using pure preparations of phosphatidate phosphatase. The 45-kDa phosphatidate phosphatase phosphorylated in vitro and in vivo had phosphopeptides in common. The activation of the GAL10-RAS2val19 allele in mutant cells resulted in an increase in the synthesis of diacylglycerols and triacylglycerols. These results were consistent with the phosphorylation and activation of 45-kDa phosphatidate phosphatase by cAMP-dependent protein kinase in vivo. 相似文献
304.
Measurement of the intramitochondrial volume in hepatocytes without cell disruption and its elevation by hormones and valinomycin. 总被引:13,自引:11,他引:2 下载免费PDF全文
Methods have been developed to measure the lysophospholipid content and matrix volume of liver cell mitochondria in situ in order to test the hypothesis that these parameters may be important in the hormonal control of mitochondrial function [Armston, Halestrap & Scott (1982) Biochim. Biophys. Acta 681, 429-439]. No change in the labelling of mitochondrial lysophospholipids with [32P]Pi was detected after treatment of liver cells with glucagon, phenylephrine or vasopressin. Incorporation of [32P]Pi into mitochondrial phosphatidylinositol was enhanced by phenylephrine and vasopressin. Mitochondrial volumes were measured using rapid disruption of cells by sonication into 3H2O and [14C]sucrose or without cell disruption using 3H2O and [14C]mannitol. In control cells the two methods gave values of 1.09 and 0.40 microliters/mg of mitochondrial protein respectively, which represent 19 and 7% respectively of the total cell volume measured with 3H2O and inulin [14C]carboxylic acid. Both methods showed that glucagon, phenylephrine and 1 nm-valinomycin produced significant increases (13% and 26% using sucrose and mannitol respectively) in mitochondrial volume. The increase was coincident with the stimulation of gluconeogenesis from L-lactate and pyruvate and of mitochondrial respiratory chain activity. The effects of glucagon and phenylephrine were additive on both mitochondrial volume and respiratory chain activity, but not on gluconeogenesis. Liver cells exposed to gluconeogenic hormones or low concentrations of valinomycin showed a decrease in light scattering at 520 nM correlating with the change in mitochondrial volume but without a change in whole-cell volume. The time course and hormone sensitivity of this response were similar to those for the hormonal stimulation of gluconeogenesis. The light-scattering response to glucagon, phenylephrine and vasopressin, but not to valinomycin, were greatly reduced or abolished in Ca2+-free media. 相似文献
305.
This study involves the use of fibroblast growth factor (FGF) as a substitute for exogenous serum to examine the early transport changes which occur when quiescent 3T3 cells re-initiate active growth. FGF, in nanogram amounts, together with insulin and dexamethasone, can induce mitogenesis and mitosis in 3T3 cells GO-arrested by holding in growth medium containing 0.8% calf serum. In terms of quiescent cell transport activity enhancement, FGF is 300,000-fold more effective than fresh serum, on a protein basis. In addition, very short exposure of serum-depleted cells to FGF indicates that a distinct temporal or time sequence exists in the transport system activation process. For example, uptake of α-aminoisobutyric acid (AIB) and uridine are stimulated very rapidly, whereas hypoxanthine uptake does not respond until much later. Closer analysis shows that AIB uptake is maximally enhanced within zero to two minutes after FGF addition to cells. Finally, the stimulatory effect of FGF on transport system activities is specific in terms of the proliferative state of the cells to which it is added, and in terms of the uptake systems which respond to it. 相似文献
306.
307.
308.
Immunological similarities between specific chloroplast ribosomal proteins from Chlamydomonas reinhardtii and ribosomal proteins from Escherichia coli 总被引:11,自引:0,他引:11
Polyclonal antibodies were elicited against seven of the 33 different
proteins of the large subunit of the chloroplast ribosome from
Chlamydomonas reinhardtii. Three of these proteins are synthesized in the
chloroplast and four are made in the cytoplasm and imported. In western
blots, six of the seven antisera are monospecific for their respective
large subunit ribosomal proteins, and none of these antisera cross-reacted
with any chloroplast small subunit proteins from C. reinhardtii. Antisera
to the three chloroplast-synthesized ribosomal proteins cross-reacted with
specific Escherichia coli large subunit proteins of comparable charge and
molecular weight. Only one of the four antisera to the chloroplast
ribosomal proteins synthesized in the cytoplasm cross-reacted with an E.
coli large subunit protein. None of the antisera cross-reacted with any E.
coli small subunit proteins. On the assumption of a procaryotic,
endosymbiotic origin for the chloroplast, those chloroplast ribosomal
proteins still synthesized within the organelle appear to have retained
more antigenic sites in common with E. coli ribosomal proteins than have
those which are now the products of cytoplasmic protein synthesis. Antisera
to this cytoplasmically synthesized group of chloroplast ribosomal proteins
did not recognize any antigenic sites among C. reinhardtii cytoplasmic
ribosomal proteins, suggesting that the genes for the cytoplasmically
synthesized chloroplast ribosomal proteins either are not derived from the
cytoplasmic ribosomal protein genes or have evolved to a point where no
antigenic similarities remain.
相似文献
309.
M D Lee G E Quinton R E Beeman A A Biehle R L Liddle D E Ellis RJ Buchanan Jr 《Journal of industrial microbiology & biotechnology》1997,18(2-3):106-115
For the full scale implementation of in situ anaerobic bioremediation of tetrachloroethene (PCE) in groundwater, the following issues must be addressed: which organic
substrates at which concentration would be most effective in promoting dechlorination and are economical; how far the substrate,
electron acceptor, and nutrients can be transported in the aquifer; and the placement of delivery and recovery wells for
distributing these amendments. In a microcosm study, almost all of the tested inexpensive substrates supported reductive
dechlorination of PCE through vinyl chloride (VC) under methanogenic conditions. A minimum of about 60 mg L−1 of organic carbon was needed to dechlorinate 23 μM PCE with a single feeding. In a second microcosm study dechlorination
stopped at 1,2-dichloroethene (DCE) in microcosms fed higher concentrations of several substrates. At the highest concentrations
the substrates inhibited DCE production. Three field tracer tests were conducted to evaluate methods to distribute the amendments
across the aquifer. The natural groundwater gradient is not sufficient to distribute substrate evenly. Groundwater injection
at 60 times the natural flux rate increased the distribution of substrate. A mixing strategy of cross-gradient injection
further increased the distribution of the substrate. Ammonia-nitrogen, sulfate, and phosphate were retarded relative to
the substrate and inorganic tracer.
Received 30 October 1995/ Accepted in revised form 07 June 1996 相似文献
310.
Five monoclonal antibodies against bacterial spores of Bacillus cereus T and Clostridium sporogenes PA3679 were developed. Two antibodies (B48 and B183) were selected for their reactivity with B. cereus T spores, two (C33 and C225) were selected for their reactivity with C. sporogenes spores, and one (D89) was selected for its reactivity with both B. cereus and C sporogenes spores. The isotypes of the antibodies were determined to be immunoglobulin G2a (IgG2a) (B48), IgG1 (B183), and IgM (C33, C225, and D89). The antibodies reacted with spores of B. cereus T, Bacillus subtilis subsp. globigii, Bacillus megaterium, Bacillus stearothermophilus, C. sporogenes, Clostridium perfringens, and Desulfotomaculum nigrificans. Antibody D89 also reacted with vegetative cells of B. cereus and C. sporogenes. Analysis of B. cereus spore extracts showed that two of the antigens with which the anti-Bacillus antibodies reacted had molecular masses of 76 kDa and approximately 250 kDa. Immunocytochemical localization indicated that antigens with which B48, B183, and D89 react are on the exosporium of the B. cereus T spore. Antibody D89 reacted with the exosporium and outer cortex of C. sporogenes spores in immunocytochemical localization studies but did not react with extracts of C. sporogenes or B. cereus spores in Western blotting. Some C. sporogenes antigens were not stable during long-term storage at -20 degrees C. Antibodies B48, B183, and D89 should prove to be useful tools for developing immunological methods for the detection of bacterial spores. 相似文献