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991.
Markus Hahn Dirk Wolters W. S. Sheldrick Frans B. Hulsbergen J. Reedijk 《Journal of biological inorganic chemistry》1999,4(4):412-420
The pH- and time-dependent reaction of [Pt(dien)(H2O)]2+ with the methionine- and histidine-containing peptides H-His-Gly-Met-OH and Ac-His-Ala-Ala-Ala-Met-NHPh at 313 K has been
investigated by HPLC and NMR spectroscopy. For both peptides, initial relatively rapid formation of the kinetically favoured
methionine S-bound complex is followed by slow intramolecular migration of the [Pt(dien)]2+ fragment to imidazole Nε
2 (or, in the case of H-His-Gly-Met-OH, to a much lesser extent to the competing imidazole Nδ
1) of the histidine side chain over a period of 500 h. Time-dependent studies for the pentapeptide at pH 8.0 demonstrate that
this isomerization can take place by either direct S→Nε
2 migration or by a two-step mechanism involving initial Nε
2 coordination of a second [Pt(dien)]2+ fragment and subsequent cleavage of the orginal Pt-S bond in the resulting dinuclear complex. The rate of κS/κN
ε
2
isomerization is markedly reduced on lowering the pH to 5.1.
Received: 26 February 1999 / Accepted: 14 April 1999 相似文献
992.
993.
Plants are multi-cellular organisms that live in diverse and fluctuating environments. Cell-cell and cell-environment com- munication are therefore critical to plant growth and develop- ment. In animals, transmembrane receptor protein tyrosine kinases play significant roles in cell-cell signaling. There was a great deal of surprise in the plant community, however, when the first receptor-like protein kinase (RLK) was isolated from maize by John C. 相似文献
994.
Jörg Barke Ryan F Seipke Sabine Grüschow Darren Heavens Nizar Drou Mervyn J Bibb Rebecca JM Goss Douglas W Yu Matthew I Hutchings 《BMC biology》2010,8(1):109
Background
Attine ants live in an intensely studied tripartite mutualism with the fungus Leucoagaricus gongylophorus, which provides food to the ants, and with antibiotic-producing actinomycete bacteria. One hypothesis suggests that bacteria from the genus Pseudonocardia are the sole, co-evolved mutualists of attine ants and are transmitted vertically by the queens. A recent study identified a Pseudonocardia-produced antifungal, named dentigerumycin, associated with the lower attine Apterostigma dentigerum consistent with the idea that co-evolved Pseudonocardia make novel antibiotics. An alternative possibility is that attine ants sample actinomycete bacteria from the soil, selecting and maintaining those species that make useful antibiotics. Consistent with this idea, a Streptomyces species associated with the higher attine Acromyrmex octospinosus was recently shown to produce the well-known antifungal candicidin. Candicidin production is widespread in environmental isolates of Streptomyces, so this could either be an environmental contaminant or evidence of recruitment of useful actinomycetes from the environment. It should be noted that the two possibilities for actinomycete acquisition are not necessarily mutually exclusive. 相似文献995.
Francesco Spinelli Antonio Cellini Joel L. Vanneste Maria T. Rodriguez-Estrada Guglielmo Costa Stefano Savioli Frans J. M. Harren Simona M. Cristescu 《Trees - Structure and Function》2012,26(1):141-152
Several analytical techniques such as gas chromatography–mass spectrometry, proton transfer reaction–mass spectrometry and
laser photoacoustic detection, were used to characterize the volatiles emitted by Erwinia amylovora and other plant-pathogenic bacteria. Diverse volatiles were found to be emitted by the different bacterial species examined.
The distinct blend of volatiles produced by bacteria allowed their identification using an electronic nose (e-nose). The present
study reports the discrimination of E. amylovora, the fire blight pathogen, from other plant-associated bacteria using an e-nose based on metal oxide semiconductor sensors.
Two different approaches were used for bacterial identification. The first one was the direct comparison of the odorous profiles
of unknown bacterial isolates with four selected reference species. The second approach was the use of previously developed
databases representing the odorous variability among several bacterial species. Using these two strategies, the e-nose successfully
identified the isolates in 87.5 and 62.5% of the cases, respectively. Finally, the profiling of the volatiles emitted by E. amylovora lead to identify some metabolic markers with a potential biological activity in vitro. 相似文献
996.
Heterologous expression of the yeast arsenite efflux system ACR3 improves Arabidopsis thaliana tolerance to arsenic stress 总被引:1,自引:0,他引:1
? Arsenic contamination has a negative impact on crop cultivation and on human health. As yet, no proteins have been identified in plants that mediate the extrusion of arsenic. Here, we heterologously expressed the yeast (Saccharomyces cerevisiae) arsenite efflux transporter ACR3 into Arabidopsis to evaluate how this affects plant tolerance and tissue arsenic contents. ? ACR3 was cloned from yeast and transformed into wild-type and nip7;1 Arabidopsis. Arsenic tolerance was determined at the cellular level using vitality stains in protoplasts, in intact seedlings grown on agar plates and in mature plants grown hydroponically. Arsenic efflux was measured from protoplasts and from intact plants, and arsenic levels were measured in roots and shoots of plants exposed to arsenate. ? At the cellular level, all transgenic lines showed increased tolerance to arsenite and arsenate and a greater capacity for arsenate efflux. With intact plants, three of four stably transformed lines showed improved growth, whereas only transgenic lines in the wild-type background showed increased efflux of arsenite into the external medium. The presence of ACR3 hardly affected tissue arsenic levels, but increased arsenic translocation to the shoot. ? Heterologous expression of yeast ACR3 endows plants with greater arsenic resistance, but does not lower significantly arsenic tissue levels. 相似文献
997.
Huang BS White RA Bi L Leenen FH 《American journal of physiology. Regulatory, integrative and comparative physiology》2012,302(7):R825-R832
Central infusion of an angiotensin type 1 (AT(1)) receptor blocker prevents sympathetic hyperactivity and hypertension in Dahl salt-sensitive (S) rats on high salt. In the present study, we examined whether central infusion of a direct renin inhibitor exerts similar effects. Intracerebroventricular infusion of aliskiren at the rate of 0.05 mg/day markedly inhibited the increase in ANG II levels in the cerebrospinal fluid and in blood pressure (BP) caused by intracerebroventricular infusion of rat renin. In Dahl S rats on high salt, intracerebroventricular infusion of aliskiren at 0.05 and 0.25 mg/day for 2 wk similarly decreased resting BP in Dahl S rats on high salt. In other groups of Dahl S rats, high salt intake for 2 wk increased resting BP by ~25 mmHg, enhanced pressor and sympathoexcitatory responses to air-stress, and desensitized arterial baroreflex function. All of these effects were largely prevented by intracerebroventricular infusion of aliskiren at 0.05 mg/day. Aliskiren had no effects in rats on regular salt. Neither high salt nor aliskiren affected hypothalamic ANG II content. These results indicate that intracerebroventricular infusions of aliskiren and an AT(1) receptor blocker are similarly effective in preventing salt-induced sympathetic hyperactivity and hypertension in Dahl S rats, suggesting that renin in the brain plays an essential role in the salt-induced hypertension. The absence of an obvious increase in hypothalamic ANG II by high salt, or decrease in ANG II by aliskiren, suggests that tissue levels do not reflect renin-dependent ANG II production in sympathoexcitatory angiotensinergic neurons. 相似文献
998.
999.
Cyclic nucleotide-gated channels (CNGCs) are a recently identified family of plant ion channels. They show a high degree of similarity to Shaker-type voltage-gated channels and contain a C-terminal cyclic nucleotide-binding domain with an overlapping calmodulin-binding domain. Heterologously expressed plant CNGCs show activation by cyclic nucleotides and permeability to monovalent and divalent cations. In plants, downstream effectors of cyclic nucleotide signals have so far remained obscure, and CNGCs might be their prime targets. The unique position of CNGCs as ligand-gated Ca(2+)-permeable channels suggests that they function at key sites where cyclic nucleotide and Ca(2+) signalling pathways interact. Such processes include plant defence responses, and two recently characterized Arabidopsis mutants in CNGC genes indeed show altered pathogen responses. 相似文献
1000.
Dynamics of cell wall structure in Saccharomyces cerevisiae 总被引:13,自引:0,他引:13
The cell wall of Saccharomyces cerevisiae is an elastic structure that provides osmotic and physical protection and determines the shape of the cell. The inner layer of the wall is largely responsible for the mechanical strength of the wall and also provides the attachment sites for the proteins that form the outer layer of the wall. Here we find among others the sexual agglutinins and the flocculins. The outer protein layer also limits the permeability of the cell wall, thus shielding the plasma membrane from attack by foreign enzymes and membrane-perturbing compounds. The main features of the molecular organization of the yeast cell wall are now known. Importantly, the molecular composition and organization of the cell wall may vary considerably. For example, the incorporation of many cell wall proteins is temporally and spatially controlled and depends strongly on environmental conditions. Similarly, the formation of specific cell wall protein-polysaccharide complexes is strongly affected by external conditions. This points to a tight regulation of cell wall construction. Indeed, all five mitogen-activated protein kinase pathways in bakers' yeast affect the cell wall, and additional cell wall-related signaling routes have been identified. Finally, some potential targets for new antifungal compounds related to cell wall construction are discussed. 相似文献