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41.
0.15 M inorganic phosphate dramatically increased the α-helix content of melittin in aqueous solution.When melittin interacted with egg yolk phosphatidylcholine liposomes in the absence of inorganic phosphate, it was converted to an α-helix rich form, as postulated by Dawson et al. (Dawson, C.R., Drake, A.F. Helliwell, J. and Hider, R.C. (1978) Biochim. Biophys. Acta 510, 75–86). 相似文献
42.
N-糖蛋白去糖基化酶(PNGase)是一种广泛存在于真菌、植物、哺乳动物中的去糖基化酶,可以水解N-糖蛋白或 N-糖肽上天冬酰胺与寡糖链连接的化学键,并释放出完整的N-寡糖。PNGase在生物体内参与蛋白质降解、器官发育、个体生长等过程。人PNGase基因功能缺陷会导致先天性去糖基化障碍,小鼠PNGase缺陷会导致胚胎致死性,线虫PNGase缺陷使其寿命下降。本文对PNGase在不同物种的分布、蛋白质结构、酶学功能及生物学功能进行阐述,为PNGase的生理病理功能及致病机制的基础研究提供思路,为PNGase作为糖生物学工具酶或药物开发的创新应用研究奠定基础。 相似文献
43.
《Journal of molecular biology》2021,433(3):166756
The pathogens Vibrio cholerae and Haemophilus influenzae use tripartite ATP-independent periplasmic transporters (TRAPs) to scavenge sialic acid from host tissues. They use it as a nutrient or to evade the innate immune system by sialylating surface lipopolysaccharides. An essential component of TRAP transporters is a periplasmic substrate binding protein (SBP). Without substrate, the SBP has been proposed to rest in an open-state, which is not recognised by the transporter. Substrate binding induces a conformational change of the SBP and it is thought that this closed state is recognised by the transporter, triggering substrate translocation. Here we use real time single molecule FRET experiments and crystallography to investigate the open- to closed-state transition of VcSiaP, the SBP of the sialic acid TRAP transporter from V. cholerae. We show that the conformational switching of VcSiaP is strictly substrate induced, confirming an important aspect of the proposed transport mechanism. Two new crystal structures of VcSiaP provide insights into the closing mechanism. While the first structure contains the natural ligand, sialic acid, the second structure contains an artificial peptide in the sialic acid binding site. Together, the two structures suggest that the ligand itself stabilises the closed state and that SBP closure is triggered by physically bridging the gap between the two lobes of the SBP. Finally, we demonstrate that the affinity for the artificial peptide substrate can be substantially increased by varying its amino acid sequence and by this, serve as a starting point for the development of peptide-based inhibitors of TRAP transporters. 相似文献
44.
《Journal of molecular biology》2021,433(4):166790
G protein coupled receptors signal through G proteins or arrestins. A long-standing mystery in the field is why vertebrates have two non-visual arrestins, arrestin-2 and arrestin-3. These isoforms are ~75% identical and 85% similar; each binds numerous receptors, and appear to have many redundant functions, as demonstrated by studies of knockout mice. We previously showed that arrestin-3 can be activated by inositol-hexakisphosphate (IP6). IP6 interacts with the receptor-binding surface of arrestin-3, induces arrestin-3 oligomerization, and this oligomer stabilizes the active conformation of arrestin-3. Here, we compared the impact of IP6 on oligomerization and conformational equilibrium of the highly homologous arrestin-2 and arrestin-3 and found that these two isoforms are regulated differently. In the presence of IP6, arrestin-2 forms “infinite” chains, where each promoter remains in the basal conformation. In contrast, full length and truncated arrestin-3 form trimers and higher-order oligomers in the presence of IP6; we showed previously that trimeric state induces arrestin-3 activation (Chen et al., 2017). Thus, in response to IP6, the two non-visual arrestins oligomerize in different ways in distinct conformations. We identified an insertion of eight residues that is conserved across arrestin-2 homologs, but absent in arrestin-3 that likely accounts for the differences in the IP6 effect. Because IP6 is ubiquitously present in cells, this suggests physiological consequences, including differences in arrestin-2/3 trafficking and JNK3 activation. The functional differences between two non-visual arrestins are in part determined by distinct modes of their oligomerization. The mode of oligomerization might regulate the function of other signaling proteins. 相似文献
45.
《Mammalian Biology》2014,79(4):230-239
Intraspecific allometric calculations of the brain to body size relation revealed distinct differences between 127 (67; 60) ancestral wild cavies and 82 (37; 45) guinea pigs, their domesticated relatives. The dependency of both measures from one another remained the same in both animal groups but the brains of guinea pigs were by 14.22% smaller at any net body weight. Consistent with results in other species the domestication of Cavia aperea is also characterized by a decrease of brain size. Fresh tissue sizes of the five brain parts medulla oblongata, cerebellum, mesencephalon, diencephalon and telencephalon were determined for 6 cavies and 6 guinea pigs by the serial section method. Additionally the sizes of 16 endbrain structures and those of the optic tract, the lateral geniculate body and the cochlear nucleus were measured. Different decrease values resulted for all these structures concomitant with domestication as was calculated from the amount of total brain size decrease and average relative structure values in the wild as well as the domesticated brain. The size decrease of the entire telencephalon (−13.7%) was within the range of the mean overall reduction as similarly was the case for the total neocortex (−10.7%) whereas the total allocortex (−20.9%) clearly was more strongly affected. The size decrease of the olfactory bulb (−41.9%) was extreme and clearly higher than found for the secondary olfactory structures (around −11%). The primary nuclei of other sensory systems (vision, audition) were decreased to less extent (lateral geniculate: −18.1%; cochlear nucleus: −12.6%). Mass decreases of pure white matter parts were nearly twice as high in contrast to associated grey matter parts (neocortex white versus grey matter; tractus opticus versus lateral geniculate body). The relatively great decrease values found for the limbic structures hippocampus (−26.9%) and schizocortex (−25.9%) are especially notable since they are in good conformity with domestication effects in other mammalian species. The findings of this study are discussed with regard to results of similar investigations on wild and domesticated gerbils (Meriones unguiculatus), the encephalization of the wild form, the special and species-specific mode and duration of domestication and in connection with certain behavioral changes as resulted from comparative investigations in ethology, socio-biology, endocrinology and general physiology. 相似文献
46.
47.
Mélody Porlier Marc Bélisle Dany Garant 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2009,364(1523):1543-1554
Improving our knowledge of the links between ecology and evolution is especially critical in the actual context of global rapid environmental changes. A critical step in that direction is to quantify how variation in ecological factors linked to habitat modifications might shape observed levels of genetic variability in wild populations. Still, little is known on the factors affecting levels and distribution of genetic diversity at the individual level, despite its vital underlying role in evolutionary processes. In this study, we assessed the effects of habitat quality on population structure and individual genetic diversity of tree swallows (Tachycineta bicolor) breeding along a gradient of agricultural intensification in southern Québec, Canada. Using a landscape genetics approach, we found that individual genetic diversity was greater in poorer quality habitats. This counter-intuitive result was partly explained by the settlement patterns of tree swallows across the landscape. Individuals of higher genetic diversity arrived earlier on their breeding grounds and settled in the first available habitats, which correspond to intensive cultures. Our results highlight the importance of investigating the effects of environmental variability on individual genetic diversity, and of integrating information on landscape structure when conducting such studies. 相似文献
48.
The cost of mutualism in a fly-fungus interaction 总被引:2,自引:0,他引:2
The movement ability of individuals has become increasingly important to a variety of ecological questions. In this study,
I investigate how plant structure and changes in body size through development affect the movement ability of a predaceous
stinkbug, Podisus maculiventris, on three species of goldenrod (Solidago spp.) representing a wide range of surface complexities. I adapt existing techniques for quantifying movement in two dimensions
to the study of movement on natural plant structures in three dimensions. These experiments indicate that plant structure
and insect size are significant factors affecting the movement ability of P. maculiventris. Changes in movement ability due to factors of ontogeny and different habitat structures suggest that the scale of an individual’s
ambit or ecological sphere of influence may vary within its lifespan. Considering the influence of ontogeny and habitat structure
on movement ability may be useful to investigations of population dynamics, foraging behavior, and pest management.
Received: 14 July 1999 / Accepted: 23 March 2000 相似文献
49.
Juan Viruel Pilar Catalán José Gabriel Segarra‐Moragues 《Journal of Biogeography》2012,39(6):1073-1085
Aim The Chilean endemic Dioscorea biloba (Dioscoreaceae) is a dioecious geophyte that shows a remarkable 600 km north–south disjunction in the peripheral arid area of the Atacama Desert. Its restricted present‐day distribution and probable Neogene origin indicate that its populations have a history linked to that of the Atacama Desert, making this an ideal model species with which to investigate the biogeography of the region. Location Chile, Atacama Desert and peripheral arid area. Methods Two hundred and seventy‐five individuals from nine populations were genotyped for seven nuclear microsatellite loci, and plastid trnL–F and trnT–L sequences were obtained for a representative subset of these. Analyses included the estimation of genetic diversity and population structure through clustering, Bayesian and analysis of molecular variance analyses, and statistical parsimony networks of chloroplast haplotypes. Isolation by distance was tested against alternative dispersal hypotheses. Results Microsatellite markers revealed moderate to high levels of genetic diversity within populations, with those from the southern Limarí Valley showing the highest values and northern populations showing less exclusive alleles. Bayesian analysis of microsatellite data identified three genetic groups that corresponded to geographical ranges. Chloroplast phylogeography revealed no haplotypes shared between northern and southern ranges, and little haplotype sharing between the two neighbouring southern valleys. Dispersal models suggested the presence of extinct hypothetical populations between the southern and northern ranges. Main conclusions Our results are consistent with prolonged isolation of the northern and southern groups, mediated by the life‐history traits of the species. Significant isolation was revealed at both large and moderate distances as gene flow was not evident even between neighbouring valleys. Bayesian analyses of microsatellite and chloroplast haplotype diversity identified the southern area of Limarí as the probable area of origin of the species. Our data do not support recent dispersal of D. biloba from the southern range into Antofagasta, but indicate the fragmentation of an earlier wider range, concomitant with the Pliocene–Pleistocene climatic oscillations, with subsequent extinctions of the Atacama Desert populations and the divergence of the peripheral ones as a consequence of genetic drift. 相似文献
50.
Gerda Saxer Michael Doebeli Michael Travisano 《Proceedings. Biological sciences / The Royal Society》2009,276(1664):2065-2070
Spatial structure has been identified as a major contributor to the maintenance of diversity. Here, we show that the impact of spatial structure on diversity is strongly affected by the ecological mechanisms maintaining diversity. In well-mixed, unstructured environments, microbial populations can diversify by production of metabolites during growth, providing additional resources for novel specialists. By contrast, spatially structured environments potentially limit such facilitation due to reduced metabolite diffusion. Using replicate microcosms containing the bacterium Escherichia coli, we predicted the loss of diversity during an environmental shift from a spatially unstructured environment to spatially structured conditions. Although spatial structure is frequently observed to be a major promoter of diversity, our results indicate that it can also have negative impacts on diversity. 相似文献