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1.
Conantokin-T (con-T) and conantokin-G (con-G) are two highly homologous peptide toxins found in Conus venom. The former is a 21-residue peptide with four gamma-carboxyglutamic acid (Gla) residues (at positions 3, 4, 10 and 14), while the latter is a 17-residue peptide with five gamma-carboxyglutamic acid residues (at positions 3, 4, 7, 10 and 14). Despite the apparent similarity in number and relative positions of the gamma-carboxyglutamic acid residues, (113)Cd-NMR studies indicated a distinct metal binding behavior for con-G and con-T. There appears to be four binding sites in con-G in contrast to one metal binding site in con-T. To elucidate the mode of calcium binding by the gamma-carboxyglutamic acid residues in these conantokins, we designed various analogous peptides with their gamma-carboxyglutamic acid replaced by other amino acid residues. (113)Cd-NMR experiments on conantokin analogues reveal that the major difference in the number of metal binding sites between con-G and con-T is due to the residue at position 7. We also performed molecular simulations to calculate the relative binding free energies of several potential binding sites. Based on our theoretical and experimental results, we propose a 'four-site' binding model for conantokin-G and a 'single-site' binding model for conantokin-T. 相似文献
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Cd2+ provokes inositol trisphosphateproduction and releases stored Ca2+, apparently by binding to a zinc site in the external domain of an orphan receptor. One pM Cd2+ evokes an immediate spike in cytosolic free Ca2+, which is similar to that evoked by bradykinin. Platelet-derived growth factor (PDGF) also increases free Ca2+ in human dermalfibroblasts, but there is a distinct lag before free Ca2+ rises in response to PDGF. Genistein, which selectively inhibits tyrosine kinases, markedly inhibited Ca2+ mobilization evoked by PDGF. Calcium mobilization triggered by cadmium or bradykinin was relatively insensitive to genistein. The PDGF receptor is known to be a tyrosine kinase, whichphosphorylates and thereby activatesphospholipase C, whereas a G protein couples the bradykinin receptor to anotherphospholipase C isoform. These findings support the hypothesis that the orphan receptor triggered by cadmium is coupled to phospholipase C via a G protein.Abbreviations BSA
bovine serum albumin
- BK
bradykinin
- [Ca2+]i
cytosolic free calcium
- DME
Dulbecco's modified Eagle's medium
- FBS
fetal bovine serum
- HEPES
4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid
- IC50
concentration that produces 50% inhibition
- PDGF
platelet-derived growth factor
- PSS
physiological salts solution
- SE
standard error of the mean 相似文献
5.
Jia An Xiang Wang Yajiang Jing Jianping Huang Qilong Wang Gang Zhang Jing Gao Liang Peng Wenli Huang Yonggang Yan 《Phyton》2023,92(5):1405-1420
Although Platycodon grandiflorum (Jacq.) A.DC. is a renowned medicine food homology plant, reports of excessive cadmium (Cd) levels are common, which affects its safety for clinical use and food consumption. To enable its Cd levels to be regulated or reduced, it is necessary to first elucidate the mechanism of Cd uptake and accumulation in the plant, in addition to its detoxification mechanisms. This present study used inductively couple plasma-mass-spectrometry to analyze the subcellular distribution and chemical forms of Cd in different tissues of P. grandiflorum. The experimental results showed that Cd was mainly accumulated in the roots [predominantly in the cell wall (50.96%–61.42%)], and it was found primarily in hypomobile and hypotoxic forms. The proportion of Cd in the soluble fraction increased after Cd exposure, and the proportion of insoluble phosphate Cd and oxalate Cd increased in roots and leaves, with a higher increase in oxalate Cd. Therefore, it is likely that root retention mechanisms, cell wall deposition, vacuole sequestration, and the formation of low mobility and low toxicity forms are tolerance strategies for Cd detoxification used by P. grandiflorum. The results of this study provide a theoretical grounding for the study of Cd accumulation and detoxification mechanisms in P. grandiflorum, and they can be used as a reference for developing Cd limits and standards for other medicine food homology plants. 相似文献
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Zhuo Yu Bingliang Wang Xiaobin Liao Kangning Zhao Zhifang Yang Fanjie Xia Congli Sun Zhuo Wang Chaoying Fan Jingping Zhang Yonggang Wang 《Liver Transplantation》2020,10(25)
Lithium–sulfur batteries have attracted extensive attention because of their high energy density. However, their application is still impeded by the inherent sluggish kinetics and solubility of intermediate products (i.e., polysulfides) of the sulfur cathode. Herein, graphene‐supported Ni nanoparticles with a carbon coating are fabricated by directly carbonizing a metal–organic framework/graphene oxide composite, which is then dispersed on a commercial glass fiber membrane to form a separator with electrocatalytic activity. In situ analysis and electrochemical investigation demonstrate that this modified separator can effectively suppress the shuttle effect and regulate the catalytic conversion of intercepted polysulfides, which is also confirmed by density functional theory calculations. It is found that Ni–C sites can chemically interact with polysulfides and stabilize the radical S3?? through Ni? S bonds to enable fast dynamic equilibrium with S62?, while Ni nanoparticles reduce the oxidation barrier of Li2S and accelerate ion/electron transport. As a result, the corresponding lithium–sulfur battery shows a high cycle stability (88% capacity retention over 100 cycles) even with a high sulfur mass loading of 8 mg cm?2 and lean electrolyte (6.25 µ L mg?1). Surprisingly, benefitting from the improved kinetics, the battery can work well at ?50 °C, which is rarely achieved by conventional Li–S batteries. 相似文献
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Yaoqi Li Peter B. Reich Bernhard Schmid Nawal Shrestha Xiao Feng Tong Lyu Brian S. Maitner Xiaoting Xu Yichao Li Dongting Zou Zheng‐Hong Tan Xiangyan Su Zhiyao Tang Qinghua Guo Xiaojuan Feng Brian J. Enquist Zhiheng Wang 《Ecology letters》2020,23(6):1003-1013
A key challenge in ecology is to understand the relationships between organismal traits and ecosystem processes. Here, with a novel dataset of leaf length and width for 10 480 woody dicots in China and 2374 in North America, we show that the variation in community mean leaf size is highly correlated with the variation in climate and ecosystem primary productivity, independent of plant life form. These relationships likely reflect how natural selection modifies leaf size across varying climates in conjunction with how climate influences canopy total leaf area. We find that the leaf size?primary productivity functions based on the Chinese dataset can predict productivity in North America and vice‐versa. In addition to advancing understanding of the relationship between a climate‐driven trait and ecosystem functioning, our findings suggest that leaf size can also be a promising tool in palaeoecology for scaling from fossil leaves to palaeo‐primary productivity of woody ecosystems. 相似文献
10.
Yang H. Y. Dong S. S. Zhang C. H. Wu W. L. Lyu L. F. Li W. L. 《Russian Journal of Plant Physiology》2020,67(1):76-84
Russian Journal of Plant Physiology - Tocopherol (vitamin E) is widely recognized as a cellular antioxidant and can prevent oxidative damage during seed quiescence and dormancy in all angiosperms.... 相似文献