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1.
Abstract Pulsed-field gel electrophoresis (PFGE) was applied to characterize Rhizobium bacteria isolated from the root nodules of Acacia senegal and Prosopis chilensis trees growing in Sudan and Keya. For the electrophoresis, the total DNA of 42 isolates, embedded in agarose, was digested by a rare-cutting restriction endonuclease, Xba I. The PFGE run resulted in good resolution of the DNA fragments and gave the strains distinctive fingerprint patterns. The patterns were analysed visually and using automated clustering analysis, which divided the strains into groups resembling the results generated by numerical taxonomy. However, several strains had unique banding patterns, which indicates that these strains are genetically very diverse. 相似文献
2.
Summary An acetyl esterase was purified from Trichoderma reesei by cation and anion exchange chromatography. The enzyme had a molecular weight of 45 000 as determined by SDS-electrophoresis, or 67 000 as determined by gel filtration. In chromatofocusing the enzyme was shown to consist of two isoenzymes with isoelectric points of 6.8 and 6.0. The enzyme showed activity towards naphthyl acetate, triacetin and glucose-and xylose acetates. However, it liberated acetic acid from acetylated xylo-oligomers only to a small extent. The liberation of acetic acid from the oligomeric substrate was enhanced by addition of endoxylanase and -xylosidase. 相似文献
3.
Abstract: Arachidonic acid and oleoylacetylglycerol enhance depolarization-evoked glutamate release from hippocampal mossy fiber nerve endings. It was proposed this is a Ca2+ -dependent effect and that protein kinase C is involved. Here we report that arachidonic acid and oleoylacetylglycerol synergistically potentiate the glutamate release induced by the Ca2+ ionophore ionomycin. The Ca2+ dependence of this effect was established, as removal of Ca2+ eliminated evoked release and the lipid-dependent potentiation. Also, Ca2+ channel blockers attenuated ionomycin- and KCI-evoked exocytosis, as well as the facilitating effects of the lipid mediators. Although facilitation required Ca2+ , it may not involve an enhancement of evoked Ca2+ accumulation, because ionomycin-dependent glutamate release was potentiated under conditions that did not increase ionomycin-induced Ca2+ accumulation. Also, the facilitation may not depend on inhibition of K+ efflux, because enhanced release was observed in the presence of increasing concentrations of 4-aminopyridine and diazoxide did not reduce the lipid-dependent potentiation of exocytosis. In contrast, disruption of cytoskeleton organization with cytochalasin D occluded the lipid-dependent facilitations of both KCI- and ionomycin-evoked glutamate release. In addition, arachidonic acid plus glutamatergic or cholinergic agonists enhanced glutamate release, whereas a role for protein kinase C in the potentiation of exocytosis was substantiated using kinase inhibitors. It appears that the lipid-dependent facilitation of glutamate release from mossy fiber nerve endings requires Ca2+ and involves multiple presynaptic effects, some of which depend on protein kinase C. 相似文献
4.
Claus-Werner Franzke Kaisa Tasanen Hauke Schumann Leena Bruckner-Tuderman 《Matrix biology》2003,22(4):299-309
Collagenous transmembrane proteins are an emerging group of biologically versatile molecules which function as both cell surface receptors and matrix molecules. The seven group members have interesting structural similarities: they are integral membrane proteins in type II orientation and have one or more collagenous domains in the extracellular C-terminus; interspersed by non-collagenous stretches which confer structural flexibility to the ectodomain. A conserved coiled-coil sequence (linker domain) immediately adjacent to the extracellular face of the cell membrane presumably serves as a nucleus for trimerization and triple-helix folding of each collagen. Intriguingly, the ectodomains of at least some of these molecules are proteolytically shed from the cell surface, releasing a shorter form of the collagen into the extracellular matrix. Collagenous transmembrane proteins are expressed in many different tissues and cells, and are involved in a broad spectrum of biological functions, reaching from epithelial and neural cell adhesion, and epithelial-mesenchymal interactions during morphogenesis to host defense against microbial agents. Several group members are involved in the molecular pathology of genetic and acquired human diseases including epidermolysis bullosa, ectodermal dysplasia, bullous pemphigoid or Alzheimer disease. An extensively investigated member is collagen XVII, a keratinocyte surface protein, which attaches the epidermis to the basement membrane in the skin. In this review, the structure and functions of the currently known collagenous transmembrane proteins are summarized and, as a 'prototype' of the group, collagen XVII and its biology and pathophysiology are delineated. 相似文献
5.
Aphelenchoides resinosi n. sp. and Ektaphelenchus joyceae n. sp. are described and illustrated from red pines of the Allegheny plateau of Maryland, USA. The new species were found in trees infested with Bursaphelenchus xylophilus. Primary diagnostic characters of A. resinosi females are constriction of the head, basal stylet knobs, tong postuterine sac, two incisures in the lateral field, and conical tail four to five anal body widths long with a simple terminal mucro. Diagnostic characters of the males are two pairs of subventral caudal papillae and spicule shape: Primary diagnostic characters of E. joyceae females are a slight constriction of the head, six similar lips, conical tail, and short postuterine sac. Diagnostic characters of the males are spicule size and shape, a single row of spermatocytes, and one pair of caudal papillae. Within-tree distributions of A. resinosi and E. joyceae are presented. A total of 70% of both red-needled and chlorotic-needled trees in the study were positive for A. resinosi and E. joyceae. Branch hierarchy was related to the percentage of samples positive for A. resinosi. 相似文献
6.
Angela Oppelt Viola H Lobert Kaisa Haglund Ashley M Mackey Lucia E Rameh Knut Liestøl Kay Oliver Schink Nina Marie Pedersen Eva M Wenzel Ellen M Haugsten Andreas Brech Tor Erik Rusten Harald Stenmark Jørgen Wesche 《EMBO reports》2013,14(1):57-64
Although phosphatidylinositol 5‐phosphate (PtdIns5P) is present in many cell types and its biogenesis is increased by diverse stimuli, its precise cellular function remains elusive. Here we show that PtdIns5P levels increase when cells are stimulated to move and we find PtdIns5P to promote cell migration in tissue culture and in a Drosophila in vivo model. First, class III phosphatidylinositol 3‐kinase, which produces PtdIns3P, was shown to be involved in migration of fibroblasts. In a cell migration screen for proteins containing PtdIns3P‐binding motifs, we identified the phosphoinositide 5‐kinase PIKfyve and the phosphoinositide 3‐phosphatase MTMR3, which together constitute a phosphoinositide loop that produces PtdIns5P via PtdIns(3,5)P2. The ability of PtdIns5P to stimulate cell migration was demonstrated directly with exogenous PtdIns5P and a PtdIns5P‐producing bacterial enzyme. Thus, the identified phosphoinositide loop defines a new role for PtdIns5P in cell migration. 相似文献
7.
Satu Mikkola Mikko Oivanen Kari Neuvonen Suvi Piitari Kaisa Ketomäki Harri Lönnberg 《Nucleosides, nucleotides & nucleic acids》2013,32(10-12):1675-1692
Abstract Uridylyl-(3′,5′)-8-carboxymethylaminoadenosine has been synthesised, and its transesterification to uridine 2′,3′-cyclic phosphate in the presence and absence of Zn2+ ion has been studied. The results show that a carboxylate function in the vicinity of the phosphodiester bond accelerates the metal ion promoted cleavage but not the metal ion independent reaction. Under acidic conditions, the predominant reaction is the cleavage of the side chain, giving the 8-amino derivative. 相似文献
8.
Jenni Liisa Rahikainen James David Evans Saara Mikander Anna Kalliola Terhi Puranen Tarja Tamminen Kaisa Marjamaa Kristiina Kruus 《Enzyme and microbial technology》2013
Non-productive cellulase adsorption onto lignin is a major inhibitory mechanism preventing enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding of enzyme–lignin interactions is essential for the development of enzyme mixtures and processes for lignocellulose hydrolysis. We have studied cellulase–lignin interactions using model enzymes, Melanocarpus albomyces Cel45A endoglucanase (MaCel45A) and its fusions with native and mutated carbohydrate-binding modules (CBMs) from Trichoderma reesei Cel7A. Binding of MaCel45A to lignin was dependent on pH in the presence and absence of the CBM; at high pH, less enzyme bound to isolated lignins. Potentiometric titration of the lignin preparations showed that negatively charged groups were present in the lignin samples and that negative charge in the samples was increased with increasing pH. The results suggest that electrostatic interactions contributed to non-productive enzyme adsorption: Reduced enzyme binding at high pH was presumably due to repulsive electrostatic interactions between the enzymes and lignin. The CBM increased binding of MaCel45A to the isolated lignins only at high pH. Hydrophobic interactions are probably involved in CBM binding to lignin, because the same aromatic amino acids that are essential in CBM–cellulose interaction were also shown to contribute to lignin-binding. 相似文献
9.
Zhi Tang Erika Bereczki Haiyan Zhang Shan Wang Chunxia Li Xinying Ji Rui M. Branca Janne Lehti? Zhizhong Guan Peter Filipcik Shaohua Xu Bengt Winblad Jin-Jing Pei 《The Journal of biological chemistry》2013,288(22):15556-15570
Previous evidence from post-mortem Alzheimer disease (AD) brains and drug (especially rapamycin)-oriented in vitro and in vivo models implicated an aberrant accumulation of the mammalian target of rapamycin (mTor) in tangle-bearing neurons in AD brains and its role in the formation of abnormally hyperphosphorylated tau. Compelling evidence indicated that the sequential molecular events such as the synthesis and phosphorylation of tau can be regulated through p70 S6 kinase, the well characterized immediate downstream target of mTor. In the present study, we further identified that the active form of mTor per se accumulates in tangle-bearing neurons, particularly those at early stages in AD brains. By using mass spectrometry and Western blotting, we identified three phosphoepitopes of tau directly phosphorylated by mTor. We have developed a variety of stable cell lines with genetic modification of mTor activity using SH-SY5Y neuroblastoma cells as background. In these cellular systems, we not only confirmed the tau phosphorylation sites found in vitro but also found that mTor mediates the synthesis and aggregation of tau, resulting in compromised microtubule stability. Changes of mTor activity cause fluctuation of the level of a battery of tau kinases such as protein kinase A, v-Akt murine thymoma viral oncogene homolog-1, glycogen synthase kinase 3β, cyclin-dependent kinase 5, and tau protein phosphatase 2A. These results implicate mTor in promoting an imbalance of tau homeostasis, a condition required for neurons to maintain physiological function. 相似文献
10.
Satu Lehti Reijo K?kel? Sohvi H?rkk? Outi Kummu Satu Helske-Suihko Markku Kupari Kalervo Werkkala Petri T. Kovanen Katariina ??rni 《PloS one》2013,8(6)
In aortic stenosis plasma lipoprotein-derived lipids accumulate in aortic valves. Here, we first compared the lipid compositions of stenotic aortic valves and atherosclerotic plaque cores. Both pathological tissues were found to be enriched in cholesteryl linoleate, a marker of extracellularly accumulated lipoproteins. In addition, a large proportion of the phospholipids were found to contain arachidonic acid, the common precursor of a number of proinflammatory lipid mediators. Next, we isolated and characterized extracellular lipid particles from human stenotic and non-stenotic control valves, and compared them to plasma lipoproteins from the same subjects. The extracellular valvular lipid particles were isolated from 15 stenotic and 14 non-stenotic aortic valves. Significantly more apoB-100-containing lipid particles were found in the stenotic than in the non-stenotic valves. The majority of the lipid particles isolated from the non-stenotic valves had sizes (23±6.2 nm in diameter) similar to those of plasma low density lipoprotein (LDL) (22±1.5 nm), while the lipid particles from stenotic valves were not of uniform size, their sizes ranging from 18 to more than 500 nm. The lipid particles showed signs of oxidative modifications, and when compared to isolated plasma LDL particles, the lipid particles isolated from the stenotic valves had a higher sphingomyelin/phosphatidylcholine –ratio, and also higher contents of lysophosphatidylcholine and unesterified cholesterol. The findings of the present study reveal, for the first time, that in stenotic human aortic valves, infiltrated plasma lipoproteins have undergone oxidative and lipolytic modifications, and become fused and aggregated. The generated large lipid particles may contribute to the pathogenesis of human aortic stenosis. 相似文献