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排序方式: 共有107条查询结果,搜索用时 31 毫秒
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Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
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Embryonic chick fibroblasts were incubated with [14C]proline and puromycin in the low concentrations of 1 to 3 mug/ml. The molecular weight of the synthesized procollagen chains, as measured by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, was progressively reduced by increasing concentrations of puromycin in this range. For example, at 3 mug/ml the great majority of the [14C]proline was contained in procollagen chains having an average molecular weight of about 95,000 instead of the control value of 125,000. Associated with this decrease in molecular weight there was a marked decrease in the incorporation of cysteine although [14C]proline incorporation was relatively unaffedted. Disulfide bond formation was drastically inhibited as was triple helix formation as measured by resistance of the procollagen to pepsin digestion. Although the shortened procollagen chains were of normal hydroxyproline content, they nevertheless were secreted much more slowly than normal procollagen. Based upon these findings, we postulate that: (a) low concentrations of puromycin terminate procollagen chains before a COOH-terminal extension is completed, (b) these COOH-terminal extensions are required for normal assembly of the three individual procollagen chains and for triple helix formation, and (c) only assembled, triple helical procollagen molecules are selected for normal secretion. 相似文献
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Sara Santarossa Alexandra R. Sitarik Christine Cole Johnson Jia Li Susan V. Lynch Dennis R. Ownby Alex Ramirez Germaine LM. Yong Andrea E. Cassidy-Bushrow 《Journal of Exercise Nutrition & Biochemistry》2021,25(4):24
[Purpose] To determine whether physical activity (PA), primarily the recommended 60 minutes of moderate-to-vigorous PA, is associated with gut bacterial microbiota in 10-year-old children.[Methods] The Block Physical Activity Screener, which provides minutes/day PA variables, was used to determine whether the child met the PA recommendations. 16S rRNA sequencing was performed on stool samples from the children to profile the composition of their gut bacterial microbiota. Differences in alpha diversity metrics (richness, Pielou’s evenness, and Faith’s phylogenetic diversity) by PA were determined using linear regression, whereas beta diversity (unweighted and weighted UniFrac) relationships were assessed using PERMANOVA. Taxon relative abundance differentials were determined using DESeq2.[Results] The analytic sample included 321 children with both PA and 16S rRNA sequencing data (mean age [SD] =10.2 [0.8] years; 54.2% male; 62.9% African American), where 189 (58.9%) met the PA recommendations. After adjusting for covariates, meeting the PA recommendations as well as minutes/day PA variables were not significantly associated with gut richness, evenness, or diversity (p ≥ 0.19). However, meeting the PA recommendations (weighted UniFrac R2 = 0.014, p = 0.001) was significantly associated with distinct gut bacterial composition. These compositional differences were partly characterized by increased abundance of Megamonas and Anaerovorax as well as specific Christensenellaceae_R-7_group taxa in children with higher PA.[Conclusion] Children who met the recommendations of PA had altered gut microbiota compositions. Whether this translates to a reduced risk of obesity or associated metabolic diseases is still unclear. 相似文献
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Cusack KP Arnold LD Barberis CE Chen H Ericsson AM Gaza-Bulseco GS Gordon TD Grinnell CM Harsch A Pellegrini M Tarcsa E 《Bioorganic & medicinal chemistry letters》2004,14(22):5503-5507
Compounds that contain an alpha,beta-unsaturated carbonyl moiety are often flagged as potential Michael acceptors. All alpha,beta-unsaturated carbonyl moieties are not equivalent, however, and we sought to better understand this system and its potential implications in drug-like molecules. Measurement of the (13)C NMR shift of the beta-carbon and correlation to in vitro results allowed compounds in our collection to be categorized as potential Michael acceptors, potential substrates for NADPH, or as photoisomerizable. 相似文献
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S Iu Kliushnik L M Selimova LM V M Za?des 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1990,(6):23-30
The optimum conditions for using the method of radioimmunoprecipitation (RIP) for the detection of human immunodeficiency virus (HIV) in serum samples have been established. Out of several available cell lines persistently infected with HIV, specially selected line 17 has been chosen. The characteristic feature of this is the high and stable (under the conditions of prolonged cultivation) accumulation of virus-specific proteins in infected cells. The optimum conditions for making the test and its evaluation have also been established. The data of literature on the advantages of the method of RIP over such traditional methods as the enzyme immunoassay and immunoblotting have been confirmed. Thus, the presence of specific antibodies in several serum samples registered as false negative has been established. The intertypical reactivity of two serotypes of the virus, HIV-1 and HIV-2, has been studied. Cross reactivity of antibodies with respect to the HIV gene gag, but not with respect to viral glycoproteids, has been established. Ideas on the expediency and prospects of using RIP for the serological control of HIV infection are presented. 相似文献
10.
Hydroxyproline stabilizes the triple helix of chick tendon collagen 总被引:10,自引:0,他引:10
S Jimenez M Harsch J Rosenbloom 《Biochemical and biophysical research communications》1973,52(1):106-114
The thermal stability of unhydroxylated procollagen relative to hydroxylated procollagen was investigated using pepsin digestion at various temperatures in the interval 15° to 35° as an enzymatic probe of conformation. The results demonstrate that the unhydroxylated molecules thermally denature between 20° and 25°, while the hydroxylated molecules are stable at least to 35°. This finding suggests that the presence of hydroxyproline in the molecule contributes significantly to the thermal stability of collagen. The results also suggest that triple strand formation may be required for normal secretion. 相似文献