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1.
Complementarity of regulation for the two glutamine synthetases from Bacillus caldolyticus, an extreme thermophile 总被引:1,自引:0,他引:1
F C Wedler D S Shreve K E Fisher D J Merkler 《Archives of biochemistry and biophysics》1981,211(1):276-287
Chromatophores from Rhodopseudomonas capsulata cells grown semiaerobically in the dark oxidize NADH, succinate, and dichlorophenolindophenol. In the presence of N3? these activities are inhibited, but light induces oxidation of dichlorophenolindophenol with O2 as a terminal electron acceptor. Cyanide also inhibits electron transport but much higher concentrations are required to inhibit the photooxidation than the dark oxidation. The photooxidation was studied in a mutant strain of Rhodopseudomonas capsulata (YIV) which cannot grow anaerobically in the light, but similarly to the wild type, grows in the presence of oxygen. Chromatophores from YIV mutant catalyze photophosphorylation and dark oxidation activities with the same properties as those of the wild type. However, the rate of photooxidation in the mutant is only one-third that of the wild type. Based on the differential inhibitor sensitivity and on the mutation it is suggested that the photooxidase is different from the two respiratory oxidases and that this photooxidation activity might be essential for growth of the cells under anaerobic conditions in the light. 相似文献
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Stephen GS Vreden Jeetendra K Jitan Rakesh D Bansie Malti R Adhin 《Memórias do Instituto Oswaldo Cruz》2013,108(8):968-973
The emerging resistance to artemisinin derivatives that has been reported in
South-East Asia led us to assess the efficacy of artemether-lumefantrine as the first
line therapy for uncomplicated Plasmodium falciparum infections in
Suriname. This drug assessment was performed according to the recommendations of the
World Health Organization in 2011. The decreasing number of malaria cases in
Suriname, which are currently limited to migrating populations and gold miners,
precludes any conclusions on artemether efficacy because adequate numbers of patients
with 28-day follow-up data are difficult to obtain. Therefore, a comparison of day 3
parasitaemia in a 2011 study and in a 2005/2006 study was used to detect the
emergence of resistance to artemether. The prevalence of day 3 parasitaemia was
assessed in a study in 2011 and was compared to that in a study in 2005/2006. The
same protocol was used in both studies and artemether-lumefantrine was the study
drug. Of 48 evaluable patients in 2011, 15 (31%) still had parasitaemia on day 3
compared to one (2%) out of 45 evaluable patients in 2005/2006. Overall, 11 evaluable
patients in the 2011 study who were followed up until day 28 had negative slides and
similar findings were obtained in all 38 evaluable patients in the 2005/2006 study.
The significantly increased incidence of parasite persistence on day 3 may be an
indication of emerging resistance to artemether. 相似文献
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Asexual reproduction is commonly thought to be associated with low genetic diversity in animals. Echmepteryx hageni (Insecta: 'Psocoptera') is one of several psocopteran species that are primarily parthenogenetic, but also exists in small, isolated sexual populations. We used mitochondrial DNA sequences to investigate the population history and genealogical relationships between the sexual and asexual forms of this species. The asexual population of E. hageni exhibits extremely high mitochondrial haplotype diversity (H=0.98), whereas the sexual forms had significantly lower haplotypic diversity (H=0.25, after correcting for sample size). This diversity in asexuals represents one the greatest genetic diversities reported for asexual animals in the literature. Nucleotide diversities were also higher in asexual compared to sexual populations (π=0.0071 vs. 0.00027). Compared to other reported estimates of π in insects, asexual nucleotide diversity is high, but not remarkably elevated. Three hypotheses might explain the elevated genetic diversity of asexual populations: (i) larger effective population size, (ii) greater mutation rate or (iii) possible recent origin of sexuals. In addition, phylogeographic analysis revealed little geographic structure among asexual E. hageni, although specimens from the upper Midwest form a single clade and are genetically differentiated. The mismatch distribution and neutrality tests indicate a historical population size increase, possibly associated with expansion from glacial refugia. 相似文献
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Kumaran Sivagnanam Vijaya GS Raghavan Manesh Shah Robert L Hettich Nathan C Verberkmoes Mark G Lefsrud 《Proteome science》2011,9(1):1-14
Background
Cytokinin is a plant hormone that plays a crucial role in several processes of plant growth and development. In recent years, major breakthroughs have been achieved in the elucidation of the metabolism, the signal perception and transduction, as well as the biological functions of cytokinin. An important activity of cytokinin is the involvement in chloroplast development and function. Although this biological function has already been known for 50 years, the exact mechanisms remain elusive.Results
To elucidate the effects of altered endogenous cytokinin content on the structure and function of the chloroplasts, chloroplast subfractions (stroma and thylakoids) from transgenic Pssu-ipt and 35S:CKX1 tobacco (Nicotiana tabacum) plants with, respectively, elevated and reduced endogenous cytokinin content were analysed using two different 2-DE approaches. Firstly, thykaloids were analysed by blue-native polyacrylamide gel electrophoresis followed by SDS-PAGE (BN/SDS-PAGE). Image analysis of the gel spot pattern thus obtained from thylakoids showed no substantial differences between wild-type and transgenic tobacco plants. Secondly, a quantitative DIGE analysis of CHAPS soluble proteins derived from chloroplast subfractions indicated significant gel spot abundance differences in the stroma fraction. Upon identification by MALDI-TOF/TOF mass spectrometry, these proteins could be assigned to the Calvin-Benson cycle and photoprotective mechanisms.Conclusion
Taken together, presented proteomic data reveal that the constitutively altered cytokinin status of transgenic plants does not result in any qualitative changes in either stroma proteins or protein complexes of thylakoid membranes of fully developed chloroplasts, while few but significant quantitative differences are observed in stroma proteins. 相似文献6.
Thiago?GazoniEmail author Simone?L?Gruber Ana?PZ?Silva Olivia?GS?Araújo Hideki?Narimatsu Christine?Strüssmann Célio?FB?Haddad Sanae?Kasahara 《BMC genetics》2012,13(1):109
Background
The karyotypes of Leptodactylus species usually consist of 22 bi-armed chromosomes, but morphological variations in some chromosomes and even differences in the 2n have been reported. To better understand the mechanisms responsible for these differences, eight species were analysed using classical and molecular cytogenetic techniques, including replication banding with BrdU incorporation.Results
Distinct chromosome numbers were found: 2n = 22 in Leptodactylus chaquensis, L. labyrinthicus, L. pentadactylus, L. petersii, L. podicipinus, and L. rhodomystax; 2n = 20 in Leptodactylus sp. (aff. podicipinus); and 2n = 24 in L. marmoratus. Among the species with 2n = 22, only three had the same basic karyotype. Leptodactylus pentadactylus presented multiple translocations, L. petersii displayed chromosome morphological discrepancy, and L. podicipinus had four pairs of telocentric chromosomes. Replication banding was crucial for characterising this variability and for explaining the reduced 2n in Leptodactylus sp. (aff. podicipinus). Leptodactylus marmoratus had few chromosomes with a similar banding patterns to the 2n = 22 karyotypes. The majority of the species presented a single NOR-bearing pair, which was confirmed using Ag-impregnation and FISH with an rDNA probe. In general, the NOR-bearing chromosomes corresponded to chromosome 8, but NORs were found on chromosome 3 or 4 in some species. Leptodactylus marmoratus had NORs on chromosome pairs 6 and 8. The data from C-banding, fluorochrome staining, and FISH using the telomeric probe helped in characterising the repetitive sequences. Even though hybridisation did occur on the chromosome ends, telomere-like repetitive sequences outside of the telomere region were identified. Metaphase I cells from L. pentadactylus confirmed its complex karyotype constitution because 12 chromosomes appeared as ring-shaped chain in addition to five bivalents.Conclusions
Species of Leptodactylus exhibited both major and minor karyotypic differences which were identified by classical and molecular cytogenetic techniques. Replication banding, which is a unique procedure that has been used to obtain longitudinal multiple band patterns in amphibian chromosomes, allowed us to outline the general mechanisms responsible for these karyotype differences. The findings also suggested that L. marmoratus, which was formerly included in the genus Adenomera, may have undergone great chromosomal repatterning.7.
Two glutamine synthetases from Bacillus caldolyticus, an extreme thermophile. Isolation, physicochemical and kinetic properties 总被引:4,自引:0,他引:4
F C Wedler D S Shreve R M Kenney A E Ashour J Carfi S G Rhee 《The Journal of biological chemistry》1980,255(19):9507-9516
Two distinctly different glutamine synthetase enzymes (EI and EII) have been isolated from the extreme thermophile Bacillus caldolyticus, grown on chemically defined medium at 70 degrees C. Purification to homogeneity mainly involves affinity chromatography and heat treatment with substrate protection. Biosynthesis of total enzyme activity can be repressed by at least 8-fold by high ammonia, with synthesis of EI being repressed more strongly than EII. A variety of chemical and biochemical tests failed to provide evidence for regulation of EI or EII by covalent modification, e.g. proteolysis, phosphorylation, or adenylylation. Neither of the thermophiic enzymes will cross-react with antibodies for the Escherichia coli or Bacillus subtilis glutamine synthetases. Both enzymes are composed of 12 subunits, each approximately 51,000 daltons. However, EI and EII differ significantly in their amino acid composition, isoelectric points (5.2 and 5.5, respectively), rates of migration on polyacrylamide electrophoresis gels at pH 6.8, and kinetic properties, EI is more active with Mg(II) than with Mn(II), but EII is more active with Mn(II) than Mg(II). Cd(II) activates EII more than EI, and only EI shows activity with Co(II). For both enzymes, the Mn(II)-stimulated activity is optimal at pH 6.0 to 6.5, with Mn(II)/ATP = 1.0, but the pH optimum with Mg(II) is near pH 7.5, however, with a ratio of Mg(II)/ATP > 2. Substrate Km values at 70 degrees C differ for EI versus EII but are quite comparable to those seen for mesophilic glutamine synthetases. Studies with structural analogs of substrates indicate that active site specificity is maintained at extreme temperatures: substitution of alpha-OH for alpha-HN2 is allowed, but unfavorable changes occur upon substitution of methyl groups for the alpha-H or onto the alpha-NH2 of L-Glu, and for D-Glu or L-Asp. EII is almost absdolutely specific for ATP, but EI can also use ITP, GTP, and UTP as substrates to some extent. The divalent metal ion that is present can affect both specificity for analogs and substrate Km values. Kinetic binding plots (v versus [S]) are biphasic for NH3 and L-Glu with the more active forms of each enzyme, EI-Mg and EII-Mn, respectively; but no positive cooperativity is observed. ATP binding is strictly hyperbolic, in contrast to the positive cooperativity previously observed with other Bacillus sp. enzymes. For purified EI and EII, Arrhenius plots are nonlinear with Mn(II) or Mg(II), exhibiting slope changes in the range of 55-65 degrees C; however, for EI-EII mixtures in crude cell extracts these plots are nearly linear. 相似文献
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L-Lactate dehydrogenase (L-LDH, E.C. 1.1.1.27) is encoded by two or three
loci in all vertebrates examined, with the exception of lampreys, which
have a single LDH locus. Biochemical characterizations of LDH proteins have
suggested that a gene duplication early in vertebrate evolution gave rise
to Ldh-A and Ldh-B and that an additional locus, Ldh-C arose in a number of
lineages more recently. Although some phylogenetic studies of LDH protein
sequences have supported this pattern of gene duplication, others have
contradicted it. In particular, a number of studies have suggested that
Ldh-C represents the earliest divergence among vertebrate LDHs and that it
may have diverged from the other loci well before the origin of
vertebrates. Such hypotheses make explicit statements about the
relationship of vertebrate and invertebrate LDHs, but to date, no closely
related invertebrate LDH sequences have been available for comparison. We
have attempted to provide further data on the timing of gene duplications
leading to multiple vertebrate LDHs by determining the cDNA sequence of the
LDH of the tunicate Styela plicata. Phylogenetic analyses of this and other
LDH sequences provide strong support for the duplications giving rise to
multiple vertebrate LDHs having occurred after vertebrates diverged from
tunicates. The timing of these LDH duplications is consistent with data
from a number of other gene families suggesting widespread gene duplication
near the origin of vertebrates. With respect to the relationships among
vertebrate LDHs, our data are not consistent with previous claims that
Ldh-C represented the earliest divergence. However, the precise
relationships among some of the main lineages of vertebrate LDHs were not
resolved in our analyses.
相似文献
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