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151.
Nonlinear relationships among evolutionary rates identify regions of functional divergence in heat-shock protein 70 genes 总被引:4,自引:0,他引:4
The neutral theory predicts that, in comparisons among related genes, the
number of amino acid replacements per site in a given gene region should be
a linear function of that in another region of the same gene, unless the
genes have diverged functionally in one region. Therefore, nonlinearity of
this relationship can be used to identify regions of possible functional
divergence among members of a multigene family. This method of analysis was
applied to members of the heat-shock protein 70 (HSP70) gene family, which
encode highly conserved ATP- dependent chaperone proteins found in all
organisms. A nonlinear relationship was found between the rate of amino
acid replacement in the conserved IA domain of the ATPase portion of the
molecule and that in other ATPase domains and the peptide-binding domain.
These results suggest that genes in the HSP70 subfamily C (dnaK of bacteria
and SSC1 of yeast) may have diverged functionally from other subfamilies in
the ATPase domains, especially IIB, whereas SSB1 of yeast has diverged
markedly in the peptide-binding domain. Functional divergence within these
regions is consistent with what is known about functional differences
between the HSP70 subfamilies in yeast.
相似文献
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154.
Background
In primates, infection is an important force driving gene evolution, and this is reflected in the importance of infectious disease in human morbidity today. The beta-defensins are key components of the innate immune system, with antimicrobial and cell signalling roles, but also reproductive functions. Here we examine evolution of beta-defensins in catarrhine primates and variation within different human populations. 相似文献155.
A. ROOME L. HILL V. AL‐FEGHALI C. G. MURNOCK J. A. GOODSELL R. SPATHIS R. M. GARRUTO 《Medical and veterinary entomology》2017,31(1):1-5
There is a public perception that the white‐tailed deer Odocoileus virginianus (Artiodactyla: Cervidae) is the main reservoir supporting the maintenance and spread of the causative agent of Lyme disease, Borrelia burgdorferi. This study examines the pathogen prevalence rate of Borrelia in adult Ixodes scapularis (Ixodida: Ixodidae), the black‐legged tick, collected from white‐tailed deer and compares it with pathogen prevalence rates in adult ticks gathered by dragging vegetation in two contiguous counties west of the Hudson Valley in upstate New York. In both Broome and Chenango Counties, attached and unattached ticks harvested from white‐tailed deer had significantly lower prevalences of B. burgdorferi than those collected from vegetation. No attached ticks on deer (n = 148) in either county, and only 2.4 and 7.3% of unattached ticks (n = 389) in Broome and Chenango Counties, respectively, were harbouring the pathogen. This contrasts with the finding that 40.8% of ticks in Broome County and 46.8% of ticks in Chenango County collected from vegetation harboured the pathogen. These data suggest that a mechanism in white‐tailed deer may aid in clearing the pathogen from attached deer ticks, although white‐tailed deer do contribute to the spatial distribution of deer tick populations and also serve as deadend host breeding sites for ticks. 相似文献
156.
D Cassel S Shoubi G Glusman E Cukierman M Rotman D Zilberstein 《Experimental parasitology》1991,72(4):411-417
We investigated the presence in Leishmania donovani promastigotes of proteins with homology to the G-proteins known to mediate signal transduction in other organisms. [alpha 32P]GTP binding experiments revealed the presence in the promastigote membrane of GTP-binding sites with high affinity and specificity. Experiments with antisera directed against mammalian G-proteins showed that the promastigotes possess a 38-kDa protein (p38) which strongly reacts with an antiserum directed against a decapeptide containing the C-terminal sequence of transducin, the G-protein that mediates visual signal transduction. The interaction of p38 with the antiserum is specifically blocked by the decapeptide antigen. p38 is enriched in plasma membranes and is absent in cytosol and in a mitochondria-enriched fraction. p38 was also detected in two other Leishmania species, L. mexicana and L. major. The migration of p38 upon sucrose gradient centrifugation of detergent extract of L. donovani membranes corresponded to Mr of approximately 70,000, indicating that p38 is part of an oligomeric structure. The findings suggest that p38 may be a component of a transmembrane signal transduction system in Leishmania. 相似文献
157.
Eimeria sinaitae n. sp. is described from the gall bladder of Agama sinaita from Wasie, Saudi Arabia. Sporulated oocysts are elongate-ellipsoid 34.4 times 22.0 (29.0–40.0 times 17.4–24.5) μm. Oocyst wall is smooth, greenish yellow, 1.2 (1.0–1.4) μm thick, and two-layered. Micropyle, polar granule, and oocyst residuum are absent. Sporocysts are ellipsoid 11.4 times 7.6 (9.8–15.0 times 6.7–9.0) μm. Sporocyst residuum is present. The sporocysts lack a Stieda body. Sporozoites are crescent-shaped, blunt at one end and tapered at the other. Eimeria species from Agamidae are compared. 相似文献
158.
Understanding the function of nocturnal song in ovenbirds: males do not countersing at night 下载免费PDF全文
Many diurnal bird species vocalize at night, however the function of nocturnal song is, generally, still poorly understood. Previous research has suggested that nocturnal song may serve a social function and is influenced by environmental factors. To test whether males attend to the nocturnal song of conspecifics, we experimentally exposed ovenbirds Seiurus aurocapilla to nocturnal flight songs, and recorded their response both during the night and during the following dawn chorus. We compared latency to song and vocal output before and after playback exposure to determine if males altered their vocalizations in response to exposure to flight songs from an unknown male. We found no evidence of counter singing or change in nocturnal song output, nor a change in vocal output during the dawn chorus following playback exposure. Our results suggest that, in ovenbirds, nocturnal song does not serve as an intraspecific social function. Nocturnal song, through rare, may be significant in the mating systems of some diurnal bird species, and requires additional study. 相似文献
159.
AL. V. Konarev V. V. Kochetkov J. A. Bailey P. R. Shewry 《Journal of Phytopathology》1999,147(2):105-108
Abstract: Water-soluble protein fractions from leaves, seeds and heads of sunflower were shown to contain inhibitors of trypsin, chymotrypsin and extracellular proteinases from Sclerotinia sclerotiorum , a pathogen of sunflower, and Colletotrichum lindemuthianum. These included bifunctional inhibitors of trypsin and subtilisin. Comparison with the patterns of inhibition of standard proteinases indicated that the major extracellular proteinases of S. sclerotiorum are subtilisin-like. It is speculated that the sunflower inhibitors play a role in conferring resistance to fungal infection. 相似文献
160.
Fibroblast-derived 3D matrix differentially regulates the growth and drug-responsiveness of human cancer cells 总被引:1,自引:0,他引:1
Ilya Serebriiskii Remedios Castell-Cros Acacia Lamb Erica A. Golemis Edna Cukierman 《Matrix biology》2008,27(6):573-585
Recent studies have emphasized the importance of cellular microenvironment in modulating cell growth and signaling. In vitro, collagen matrices, Matrigel, and other synthetic support systems have been used to simulate in vivo microenvironments, and epithelial cells grown in these matrices manifest significant differences in proliferation, differentiation, response to drugs, and other parameters. However, these substrates do not closely resemble the mesenchymal microenvironment that is typically associated with advanced carcinomas in vivo, which is produced to a large extent by fibroblasts. In this study, we have evaluated the ability of a fibroblast-derived three-dimensional matrix to regulate the growth of a panel of 11 human tumor epithelial cell lines. Although proliferative and morphological responses to three-dimensional cues segregated independently, general responsiveness to the matrix correlated with the ability of matrix to influence drug responses. Fibroblast-derived three-dimensional matrix increased beta1-integrin-dependent survival of a subset of human cancer cell lines during taxol treatment, while it sensitized or minimally influenced survival of other cells. beta1-integrin-dependent changes in cell resistance to taxol did not correlate with the degree of modulation of FAK and Akt, implying that additional signaling factors are involved. Based on these results, we propose that these matrices potentially have value as in vitro drug screening platforms. 相似文献