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91.
Conrad C. Labandeira Qiang Yang Jorge A. Santiago-Blay Carol L. Hotton Antónia Monteiro Yong-Jie Wang Yulia Goreva ChungKun Shih Sandra Siljestr?m Tim R. Rose David L. Dilcher Dong Ren 《Proceedings. Biological sciences / The Royal Society》2016,283(1824)
Mid-Mesozoic kalligrammatid lacewings (Neuroptera) entered the fossil record 165 million years ago (Ma) and disappeared 45 Ma later. Extant papilionoid butterflies (Lepidoptera) probably originated 80–70 Ma, long after kalligrammatids became extinct. Although poor preservation of kalligrammatid fossils previously prevented their detailed morphological and ecological characterization, we examine new, well-preserved, kalligrammatid fossils from Middle Jurassic and Early Cretaceous sites in northeastern China to unravel a surprising array of similar morphological and ecological features in these two, unrelated clades. We used polarized light and epifluorescence photography, SEM imaging, energy dispersive spectrometry and time-of-flight secondary ion mass spectrometry to examine kalligrammatid fossils and their environment. We mapped the evolution of specific traits onto a kalligrammatid phylogeny and discovered that these extinct lacewings convergently evolved wing eyespots that possibly contained melanin, and wing scales, elongate tubular proboscides, similar feeding styles, and seed–plant associations, similar to butterflies. Long-proboscid kalligrammatid lacewings lived in ecosystems with gymnosperm–insect relationships and likely accessed bennettitalean pollination drops and pollen. This system later was replaced by mid-Cretaceous angiosperms and their insect pollinators. 相似文献
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94.
Kapralov AA Kurnikov IV Vlasova II Belikova NA Tyurin VA Basova LV Zhao Q Tyurina YY Jiang J Bayir H Vladimirov YA Kagan VE 《Biochemistry》2007,46(49):14232-14244
Activation of peroxidase catalytic function of cytochrome c (cyt c) by anionic lipids is associated with destabilization of its tertiary structure. We studied effects of several anionic phospholipids on the protein structure by monitoring (1) Trp59 fluorescence, (2) Fe-S(Met80) absorbance at 695 nm, and (3) EPR of heme nitrosylation. Peroxidase activity was probed using several substrates and protein-derived radicals. Peroxidase activation of cyt c did not require complete protein unfolding or breakage of the Fe-S(Met80) bond. The activation energy of cyt c peroxidase changed in parallel with stability energies of structural regions of the protein probed spectroscopically. Cardiolipin (CL) and phosphatidic acid (PA) were most effective in inducing cyt c peroxidase activity. Phosphatidylserine (PS) and phosphatidylinositol bisphosphate (PIP2) displayed a significant but much weaker capacity to destabilize the protein and induce peroxidase activity. Phosphatidylinositol trisphosphate (PIP3) appeared to be a stronger inducer of cyt c structural changes than PIP2, indicating a role for the negatively charged extra phosphate group. Comparison of cyt c-deficient HeLa cells and mouse embryonic cells with those expressing a full complement of cyt c demonstrated the involvement of cyt c peroxidase activity in selective catalysis of peroxidation of CL, PS, and PI, which corresponded to the potency of these lipids in inducing cyt c's structural destabilization. 相似文献
95.
Glukhov E Shulga YV Epand RF Dicu AO Topham MK Deber CM Epand RM 《Biochimica et biophysica acta》2007,1768(10):2549-2558
Diacylglycerol kinase epsilon (DGKepsilon) is unique among mammalian DGK isoforms in having a segment of hydrophobic amino acids as a putative membrane anchor. To model the conformation, and stoichiometry of this segment in membrane-mimetic environments, we have prepared a peptide corresponding to this hydrophobic segment of DGKepsilon of sequence KKKKLILWTLCSVLLPVFITFWKKKKK-NH(2). Flanking Lys residues mimic the natural setting of this peptide in DGKepsilon, while facilitating peptide synthesis and characterization. Circular dichroism and fluorescence spectroscopic analysis demonstrated that the peptide has increased helical content and significant blue shifts in the presence of anionic--but not zwitterionic--bilayer membranes. When labeled with fluorophores that can undergo fluorescence resonance energy transfer, the peptide was found to dimerize--a result also observed from migration rates on SDS-PAGE gels under both reducing and non-reducing disulfide bridge conditions. The peptide was shown to preferentially interact with cholesterol in lipid films comprised of homogeneous mixtures of cholesterol and phosphatidylcholine, yet the presence of cholesterol in hydrated vesicle bilayers decreases its helical content. The peptide was also able to inhibit the activity of DGKepsilon protein in vitro. Our overall findings suggest that the peptide ultimately cannot leave the bulk water for attachment/insertion into the outer leaflet of an erythrocyte-like bilayer, yet its core sequence is sufficiently hydrophobic to insert into membrane core regions when membrane attachment is promoted by electrostatic attraction to anionic lipid head groups of the inner leaflet of an erythrocyte-like bilayer. 相似文献
96.
Two Radix spp. (Gastropoda: Lymnaeidae) endemic to thermal springs around Lake Baikal represent ecotypes of the widespread Radix auricularia
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Olga Aksenova Maxim Vinarski Ivan Bolotov Alexander Kondakov Yulia Bespalaya Alyona Tomilova Inga Paltser Mikhail Gofarov 《Journal of Zoological Systematics and Evolutionary Research》2017,55(4):298-309
In this study, we re‐examine two species of freshwater gastropods of the genus Radix Montfort, 1810 (family Lymnaeidae), endemic to the geothermal springs in the Lake Baikal region in the southern part of eastern Siberia — Lymnaea (Radix) hakusyensis Kruglov et Starobogatov, 1989, and Lymnaea (Radix) thermobaicalica Kruglov et Starobogatov, 1989. The alleged species status of these endemics has been re‐assessed by means of an integrative approach combining molecular genetic taxonomy techniques with the traditional methods based on shell and soft body morphology. Phylogenetic reconstructions were made using both mitochondrial (COI) and nuclear (ITS2) DNA markers. We used topotypic samples of both species and specimens sampled from other sites around Lake Baikal. The results demonstrate that the two endemic species are only synonyms of a widespread Holarctic species, Radix auricularia (Linnaeus, 1758), and represent its intraspecific morph (ecotype) adapted to living in thermal springs. A new synonymy is proposed: Thermoradix Kruglov et Starobogatov, 1989 = Radix Montfort, 1810 (syn. n.). 相似文献
97.
Unloading of homologous recombination factors is required for restoring double‐stranded DNA at damage repair loci
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Yulia Vasianovich Veronika Altmannova Oleksii Kotenko Matthew D Newton Lumir Krejci Svetlana Makovets 《The EMBO journal》2017,36(2):213-231
Cells use homology‐dependent DNA repair to mend chromosome breaks and restore broken replication forks, thereby ensuring genome stability and cell survival. DNA break repair via homology‐based mechanisms involves nuclease‐dependent DNA end resection, which generates long tracts of single‐stranded DNA required for checkpoint activation and loading of homologous recombination proteins Rad52/51/55/57. While recruitment of the homologous recombination machinery is well characterized, it is not known how its presence at repair loci is coordinated with downstream re‐synthesis of resected DNA. We show that Rad51 inhibits recruitment of proliferating cell nuclear antigen (PCNA), the platform for assembly of the DNA replication machinery, and that unloading of Rad51 by Srs2 helicase is required for efficient PCNA loading and restoration of resected DNA. As a result, srs2Δ mutants are deficient in DNA repair correlating with extensive DNA processing, but this defect in srs2Δ mutants can be suppressed by inactivation of the resection nuclease Exo1. We propose a model in which during re‐synthesis of resected DNA, the replication machinery must catch up with the preceding processing nucleases, in order to close the single‐stranded gap and terminate further resection. 相似文献
98.
Thevelein JM Bonini BM Castermans D Haesendonckx S Kriel J Louwet W Thayumanavan P Popova Y Rubio-Texeira M Schepers W Vandormael P Van Zeebroeck G Verhaert P Versele M Voordeckers K 《Acta microbiologica et immunologica Hungarica》2008,55(2):75-89
In yeast the Protein Kinase A (PKA) pathway can be activated by a variety of nutrients. Fermentable sugars, like glucose and sucrose, trigger a spike in the cAMP level, followed by activation of PKA and phosphorylation of target proteins causing a.o. mobilization of reserve carbohydrates, repression of stress-related genes and induction of growth-related genes. Glucose and sucrose are sensed by a G-protein coupled receptor system that activates adenylate cyclase and also activates a bypass pathway causing direct activation of PKA. Addition of other essential nutrients, like nitrogen sources or phosphate, to glucose-repressed nitrogen- or phosphate-starved cells, also triggers rapid activation of the PKA pathway. In these cases cAMP is not involved as a second messenger. Amino acids are sensed by the Gap1 transceptor, previously considered only as an amino acid transporter. Recent results indicate that the amino acid ligand has to induce a specific conformational change for signaling. The same amino acid binding site is involved in transport and signaling. Similar results have been obtained for Pho84 which acts as a transceptor for phosphate activation of the PKA pathway. Ammonium activation of the PKA pathway in nitrogen-starved cells is mediated mainly by the Mep2 transceptor, which belongs to a different class of transporter proteins. Hence, different types of sensing systems are involved in control of the yeast PKA pathway by nutrients. 相似文献
99.
Fibroblast growth factor (FGF)-activated signaling regulates an array of cellular processes ranging from embryonic development to tissue repair. A recent paper by Murakami et al. identifies a potentially important role for FGF signaling in maintenance of endothelial barrier homeostasis through the regulation of adherens junctions. 相似文献
100.
Zein S Kulik LV Yano J Kern J Pushkar Y Zouni A Yachandra VK Lubitz W Neese F Messinger J 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2008,363(1494):1167-77; discussion 1177
Nature invented a catalyst about 3Gyr ago, which splits water with high efficiency into molecular oxygen and hydrogen equivalents (protons and electrons). This reaction is energetically driven by sunlight and the active centre contains relatively cheap and abundant metals: manganese and calcium. This biological system therefore forms the paradigm for all man-made attempts for direct solar fuel production, and several studies are underway to determine the electronic and geometric structures of this catalyst. In this report we briefly summarize the problems and the current status of these efforts and propose a density functional theory-based strategy for obtaining a reliable high-resolution structure of this unique catalyst that includes both the inorganic core and the first ligand sphere. 相似文献