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11.
The presence of Ca2+-ATPase activities with high-affinity sites for Ca2+ in brush border as well as basolateral plasma membranes of rat duodenal epithelium has been reported previously (Ghijsen, W.E.J.M. and van Os, C.H. (1979) Nature 279, 802–803). Since both plasma membranes contain alkaline phosphatase (EC 3.1.3.1), which also can be stimulated by Ca2+, the substrate specificity of Ca2+-induced ATP-hydrolysis has been studied to determine whether or not alkaline phosphatase and Ca2+-ATPase are two distinct enzymes. In basolateral fragments, the rate of Ca2+-dependent ATP-hydrolysis was greater than that of ADP, AMP and at Ca2+ concentrations below 25 μM. At 0.2 mM Ca2+ the rates of ATP, ADP, AMP and hydrolysis were not significantly different. In brush border fragments the rates of ATP, ADP and AMP hydrolysis were identical at low Ca2+, but at 0.2 mM Ca2+, Ca2+-induced hydrolysis of ADP and AMP was greater than either ATP or . Alkaline phosphatase in brush border and basolateral membranes was inhibited by 75% after addition of 2.5 mM theophylline. Ca2+-stimulated ATP hydrolysis at 1 μM Ca2+ was not sensitive to theophylline in basolateral fragments while the same activity in brush border fragments was totally inhibited. At 0.2 mM Ca2+, Ca2+-induced ATP hydrolysis in both basolateral and brush border membranes was sensitive to theophylline. Oligomycin and azide had no effect on Ca2+-stimulated ATP hydrolysis, either at low or at high Ca2+ concentrations. Chlorpromazine fully inhibited Ca2+-stimulated ATP hydrolysis in basolateral fragments at 5 μM Ca2+, while it had no effect in brush border fragments. From these results we conclude that, (i) Ca2+-ATPase and alkaline phosphatase are two distinct enzymes, (ii) high-affinity Ca2+-ATPase is exclusively located in basolateral plasma membranes, (iii) alkaline phosphatase activity, present on both sides of duodenal epithelium, is stimulated slightly by low Ca2+ concentrations, but this Ca2+-induced activity is inhibited by theophylline and shows no specificity with respect to ATP, ADP or AMP. 相似文献
12.
G J Hughes C de Jong R W Fischer K H Winterhalter K J Wilson 《The Biochemical journal》1981,199(1):61-67
Native rat haemoglobins were found to bind simetryn sulphoxide to an extent 40-fold greater than human haemoglobin. This specific behaviour was studied by using only high-pressure ('performance') liquid chromatography for the preparative separation of globin chains and the isolation of peptides resulting from chemical and enzymic degradation. High recoveries (greater than 80%) of peptides throughout the procedures in combination with microsequence techniques, allow a definitive assignment of the residue undergoing modification. The haemoglobin beta-chain cystine-125 residue, with a stoichiometry of one per tetramer of rat haemoglobin, was found to be modified. Stereochemical implications of this finding are discussed. Simetryn sulphoxide would appear to be useful as a specific reagent for the mapping of exposed thiol residues in proteins. 相似文献
13.
The present report describes two female siblings of mixed ancestry (Cape Coloured) with consanguineous parents as further examples of Cross oculocerebral hypopigmentation syndrome. The mixed pattern of hair pigmentation as an important diagnostic sign is emphasized. 相似文献
14.
The influx of [14C]isethionate (ISA) into rat brain slices was studied with and without taurine. This influx was relatively rapid, but took place largely by a non-saturable, passive mechanism, which transferred much less ISA into the brain cells than taurine. Taurine inhibited the influx of ISA competitively (K
m=50 and 100 mol/l) at low ISA concentrations, and ISA that of taurine non-competitively (V=200 and 400–700 mol×min–1×kg–1 wet weight) at high taurine concentrations. It thus appears that ISA and taurine may have a small number of common transport sites at brain cell membranes, but these are apparently of little significance for the total transport of ISA. 相似文献
15.
Wilfried W. de Jong Louis H. Cohen Jack A.M. Leunissen Anneke Zweers 《Biochemical and biophysical research communications》1980,96(2):648-655
αAIns, an elongated α-crystallin A chain previously observed in rat, was present beside the normal αA chain in mouse, gerbil and hamster, which places its origin at least 30 million years ago. Like in rat the sequences of golden hamster αAIns and αA were found to be identical, apart from the internal insertion of 22 residues in αAIns. The hamster chains only differed from the rat chains by a single substitution in the inserted sequence of αAIns. The origin of αAIns, by insertion of 22 residues in an otherwise unchanged αA chain, and its rigid evolutionary conservation are most easily explained by assuming the incomplete removal of a putative intervening sequence from the precursor mRNA of αA, leaving an intracistronic insert of 66 nucleotides in part of the eventually translated mRNA. 相似文献
16.
More than 300 reference strains representing 60 species and varieties ofFusarium cultures named according to different taxonomic systems are currently maintained at the American Type Culture Collection (ATCC). They have been preserved by freeze-drying and by freezing and subsequent storage in liquid nitrogen (–196°C) to insure their viability without contamination, variation, mutation, or deterioration. The materials and procedures used at the ATCC for the acquisition, accessioning, cataloguing, preservation and distribution are described. Longevity storage data for the strains available for distribution are presented and discussed. 相似文献
17.
Non-ideal miscibility in the liquid phase of mono- or diglycerides with triglycerides has been described in terms of thermodynamic excess functions. To this end the heat of mixing and the solubility temperatures of several ideal and non-ideal binary glyceride mixtures have been measured. The non-ideal phase behaviour of glyceride systems reported in the literature has been satisfactorily predicted, which indicates that the excess functions are generally applicable to mixtures of mono- or diglycerides with triglycerides. 相似文献
18.
Evaluation of Bottlenecks in the Late Stages of Protein Secretion in Bacillus subtilis 总被引:3,自引:0,他引:3 下载免费PDF全文
Albert Bolhuis Harold Tjalsma Hilde E. Smith Anne de Jong Rob Meima Gerard Venema Sierd Bron Jan Maarten van Dijl 《Applied microbiology》1999,65(7):2934-2941
Despite a high capacity for secretion of homologous proteins, the secretion of heterologous proteins by Bacillus subtilis is frequently inefficient. In the present studies, we have investigated and compared bottlenecks in the secretion of four heterologous proteins: Bacillus lichenifomis α-amylase (AmyL), Escherichia coli TEM β-lactamase (Bla), human pancreatic α-amylase (HPA), and a lysozyme-specific single-chain antibody. The same expression and secretion signals were used for all four of these proteins. Notably, all identified bottlenecks relate to late stages in secretion, following translocation of the preproteins across the cytoplasmic membrane. These bottlenecks include processing by signal peptidase, passage through the cell wall, and degradation in the wall and growth medium. Strikingly, all translocated HPA was misfolded, its stability depending on the formation of disulfide bonds. This suggests that the disulfide bond oxidoreductases of B. subtilis cannot form the disulfide bonds in HPA correctly. As the secretion bottlenecks differed for each heterologous protein tested, it is anticipated that the efficient secretion of particular groups of heterologous proteins with the same secretion bottlenecks will require the engineering of specifically optimized host strains. 相似文献
19.
Riboprinting was used to determine the relationships among strains belonging to 15 species of the genusKluyveromyces. The small subunit ribosomal RNA gene (SSU rDNA) was amplified using the Polymerase Chain Reaction (PCR) and subjected to a battery of nine restriction enzymes. Similarity coefficients between strains were calculated based on shared and unique restriction fragments. Cluster analysis revealed three major groups that generally correlated with previously reported relationships based on other molecular data. Variations in SSU rDNA restriction fragments may be used for differentiation of theKluyveromyces strains included in this study.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
20.
So Eun Park Jong Cheol Kim Se Jin Lee Mi Rong Lee Sihyeon Kim Dongwei Li Sehyeon Baek Ji Hee Han Jeong Jun Kim Kyung Bon Koo Tae Young Shin Jae Su Kim 《Journal of Asia》2018,21(4):1102-1109
Entomopathogenic fungi have great potential to control agricultural and horticultural insect pests, however optimizing conidial production systems to demonstrate high productivity and stability still needs additional efforts for successful field application and industrialization. Although many virulent entomopathogenic fungal isolates have been viewed as potential candidates in a laboratory environment, very few of the isolates are being used in practice for application in agricultural fields as commercial products. I. javanicus is an entomopathogenic fungus that is parasitic to various diverse coleopteran and lepidopteran insects and thought good candidate as biopesticdes. In this work, the basic characteristics of two entomopathogenic fungi, I. javanica FG340 and Pf04, were investigated in morphological examinations, genetic identification, and virulence against Thrips palmi, and then the feasibility of various grains substrates for conidial production was assessed, particularly focusing on conidial productivity and thermotolerance. Isaria javanica FG340 and Pf04 conidia were solid-cultured on 12 grains for 14?days in a Petri dish. Of the tested Italian millet, perilla seed, millet and barley-based cultures showed high conidial production. The four-grain media yielded >1?×?109 conidia/g of I. javanica FG340 and Pf04. Pf04 strain had enhanced thermotolerance up to 45?°C when cultured on Italian millet. In application, it was easy to make a conidial suspension using the cultured grains, and several surfactants were tested to release the conidia. This work suggests several possible inexpensive grain substrates by which to promote conidial production combined with enhanced stability against exposure to high temperature. 相似文献