Altered copper metabolism in cultured cells from human Menkes' syndrome and mottled mouse mutants

Cultured cells of a variety of different types from human Menkes' syndrome patients and brindled mouse mutants exhibit similarly altered responses to changes in extracellular copper concentration. This suggests that the mutations in the mouse and human are very similar and that mutant gene expression is occurring in many different tissues. Intracellular copper levels are markedly elevated in mutant cells in normal medium and in medium containing a hundredfold higher copper. Some cell lines from heterozygotes possess elevated copper levels. Elevated extracellular copper and zinc are significantly more toxic to mutant cells. Mutant cells exhibit normal rates of uptake of copper-64 over a 10-min period but abnormally high accumulation over 24 hr and low rates of efflux. Menkes' fibroblasts become saturated with copper-64 at lower extracellular concentrations than for normal fibroblasts. These data support the idea of enhanced intracellular binding in mutant cells.This work was supported by grants from the Australian National Health and Medical Research Council, the McPherson/Shutt Trust, and the Apex Foundation.     

Mode of action of a bacteriocin produced byEnterobacter cloacae DF 13

Enterobacter cloacae DF 13 produces a bacteriocin with killing action onKlebsiella edwardsii var.edwardsii. The degree of sensitivity to the bacteriocin depended on the medium in which the cells were grown and on the bacteriocin concentration used. An excess of bacteriocin (60 K.U./ml) arrested growth in about 60 min. Growth of bacteriocin-treated cultures could be restored by trypsin treatment. In Brain Heart Infusion cultures trypsin rapidly restored bacterial growth even after 60 min of bacteriocin treatment. However, in broth cultures and minimal medium cultures treated with bacteriocin for only 10 min, it took 4 to 5 hr before growth started again. The bacteriocin had little effect on resting cells. Broth-grown cells had about 280 and BHI-grown cells about 340 bacteriocin receptor sites. Bacteriocin DF 13 strongly inhibited protein synthesis after a lag-time of 15 to 60 min depending on the concentration used but had no effect on RNA and DNA synthesis nor on respiration and fermentation. The bacteriocin stimulated RNA synthesis in a leucine-deficient mutant after leucine deprivation.We are grateful to W. Schipper and H. R. de Jonge for assistence in some experiments. The investigations were supported (in part) by the Netherlands Foundation for Chemical Research (SON) with financial aid from the Netherlands Organization for the Advancement of Pure Research (ZWO).     

Optimized extracellular production of alkaline phosphatase by lky mutants of Escherichia coli K12

Summary Periplasmic-leaky (lky) Hfr mutant strains of Escherichia coli K12, grown in low-phosphate Tris medium, excreted alkaline phosphatase (AP) into the extracellular fluid. The lky207 mutation, which proved to induce the highest AP excretion rate, was transferred to an F^- host, carrying a phoS, T mutation allowing constitutive AP biosynthesis. Use of high-phosphate LB-rich medium for growing this F^- lky strain improved cell biomass, extracellular AP activity and excretion specificity in favour of the enzyme. Physiological studies helped us to develop a new culture medium (LB 8.3) giving higher enzyme and excretion yields. LB 8.3 medium also increased cell viability of lky mutants stored at 4° C.Using optimized culture conditions, the highest extracellular enzyme activity produced by lky mutant 706 was reached in the late stationary growth phase and was equal to 1,400 U/ml of culture medium (i.e., 6 times the intracellular AP content of wild-type strain, Ga15, developed in derepressed conditions); AP released into the extracellular fluid corresponded to 34% of total excreted proteins and was equivalent to a purified enzyme preparation.     

Characterization of a pyoverdine-deficient mutant of Pseudomonas fluorescens impaired in the secretion of extracellular lipase

A mutant of Pseudomonas fluorescens strain B52 deficient in the synthesis of the fluorescent pigment, pyoverdine, was isolated. Absence of pyoverdine and other siderophores was confirmed by gel filtration, a specific siderophore assay, and inhibition studies with the iron chelator EDDA. Both parent and mutant synthesized additional outer membrane proteins in response to iron-limitation. Mutant cells cultured in the absence of iron(III) accumulated ⁵⁵Fe-labeled pyoverdine. The mutant produced extracellular proteinase normally on various media, but was deficient in lipase secretion. Growth of the mutant with partially-purified pyoverdine resulted in a 2.5-fold stimulation of lipase secretion. The mutant grew poorly in deferrated medium; however, the addition of iron(III) stimulated growth. Proteinase secretion in deferrated medium was stimulated over a narrow range of iron(III) concentration, while lipase secretion was only slightly affected. The data suggest that separate regulatory mechanisms exist for the control of proteinase and lipase secretion by iron(III).Contribution No. 768 from the Food Research Centre     

In vitro mitochondrial complementation in Neurospora crassa

Mitochondrial isoleucine-valine biosynthesis in strain 330a, an iv-1 mutant of Neurospora, is blocked at the dihydroxy acid dehydration step owing to a mutation in the nuclear structural gene for the specific enzyme dihydroxy acid dehydratase. Dehydratase purified from either the soluble or the mitochondrial fraction of wild-type Neurospora, and incubated in vitro with 330a mitochondria, restores valine synthesis from pyruvate-C ¹⁴ to wild type levels. Up to 29% of the restored synthesis could be attributed to the penetration of enzyme into the mitochondria. However, the bulk of the restored synthesis was found to be mediated via the secretion of dihydroxyvaline (DHV) by the mitochondria into the assay milieu, with subsequent enzymatic catalysis of this metabolite to ketovaline occurring outside the organelle. The ketovaline apparently diffuses back into mitochondria for final transamination to valine. This shunting of valine precursors in and out of mitochondria has been demonstrated to be the mechanism whereby two different populations of mitochondria isolated from mutants 330a and 305A (an iv-2 mutant lacking a functional reductoisomerase) can complement each other for the biosynthesis of valine, even when each population is enclosed in a separate dialysis bag. This observation provides the basis for a biochemical understanding of the growth complementation at the organismic level when these two iv-requiring mutants are cultured together in minimal medium.Work supported by grants GM 12323 and 2TO1 GM 00337 from the National Institutes of Health, USPHS, and a grant from the Robert A. Welch Foundation, Houston, Texas.     

Effect of environmental conditions on the production of two extracellular proteolytic enzymes byVibrio SA1

The production of two extracellular proteases, an endopeptidase and an aminopeptidase, by the marine bacteriumVibrio SA1 was studied in batch cultures. The production of the proteases was induced during growth of the organism in peptone media and by several amino acids during growth in minimal media. It was repressed by easily metabolisable carbon compounds such as glucose, lactate and succinate during growth in peptone media. During growth in a lactate basal medium, phenylalanine was one of the best inducers and this amino acid was therefore used in further experiments. That lactate dit not repress the synthesis of the proteases during growth in the lactate basal medium supplemented with 2mm phenylalanine as an inducer, appeared to be a consequence of the low iron content of this medium. Growth curves ofVibrio SA1 on such media showed a period of linear growth during which protease production was observed. When the iron concentration was made sufficiently high to prevent linear growth, the synthesis of the proteases remained repressed. Apparently by imposing an iron limitation on the organism, catabolite repression by lactate was relieved. Similarly, when growth was limited by very low values of the dissolved oxygen tension in the medium, a high rate of protease synthesis was found which was immediately repressed when the oxygen limitation was released. The results indicate that the growth rate and/or a factor associated with the energy metabolism play a role in the regulation of the synthesis of the enzymes.This study was supported by the Foundation for Fundamental Biological Research (BION), which is subsidised by the Netherlands Organization for the Advancement of Pure Research (ZWO).     

Deficiency of dihydroxy acid dehydratase in the mito-chondria of the iv-1 mutants of Neurospora crassa

The isoleucine-valine requiring mutants of Neurospora crassa which map at the iv-1 locus lack, or have a very low level of activity for, the enzyme dihydroxy acid dehydratase in the mitochondrial fractions derived from them. This enzyme is, however, present in the soluble fractions of the mutant homogenates. The enzyme is present in both mitochondrial and soluble fractions from homogenates of wild-type and from homogenates of iv mutants blocked at other steps in the isoleucine-valine pathway.The work reported here was supported in part by grants GM 12323 and 5TO1-GM-00337-09 from the National Institutes of Health, United States Public Health Service, and by a grant from the Robert A. Welch Foundation.Recipient of Research Career Award 4-K-6-GM-18,383 from the National Institutes of Health, United States Public Health Service.     

Subcellular location of the tetrapyrrole synthesis enzyme porphobilinogen deaminase in higher plants: an immunological investigation

A recombinant plasmid, pArab8, harbouring the cDNA encoding the mature form of the tetrapyrrole synthesis enzyme porphobilinogen deaminase (EC 4.3.1.8; also known as hydroxymethylbilane synthase) from Arabidopsis thaliana (L.) Heynh. has been constructed, and used to transform Escherichia coli. The porphobilinogen deaminase protein from Arabidopsis was overexpressed in this strain, and purified to homogeneity (3000-fold) with a yield of 20%. Antibodies were raised against the purified plant enzyme, and used in Western blot analysis, immunoprecipitation of enzyme activity and immuno-gold electron microscopy. The results indicate that the enzyme is confined to plastids in both leaves and roots. The implications of this finding for plant tetrapyrrole synthesis are discussed.Abbreviations DEAE diethylaminoethyl - FPLC fast protein liquid chromatography - PBG porphobilinogen This work was supported by Science and Engineering Research Council (SERC) and Agricultural and Food Research Council (AFRC) grants to P.M.J. and an AFRC grant to A.G.S. The protein sequencing was carried out by Mr Lawrence Hunt of the SERC MRI Protein Sequencing Unit (Director Dr M.G. Gore) at Southampton University. We acknowledge the Wellcome Foundation for financial support of the Protein and Nucleic Acid Chemistry Facility at the University of Cambridge, where the oligonucleotide primers were synthesised.     

The Effect of the Plant Growth Stimulant Bactozole on Rhizobium leguminosarum bv. viciae 250a and Its Nitrogen-Tolerant Mutant M-71 under Different Nitrogen Supply Conditions

The effect of the plant growth stimulant bactozole on the growth of Rhizobium leguminosarum bv. viciae 250a and its nitrogen-tolerant mutant M-71 and the synthesis of extracellular carbohydrates was studied. At a low content of nitrate (6 mM) in the medium, all three bactozole concentrations tested (0.001, 0.01, and 0.1%) exerted similar stimulating effects on the growth of the parent strain 250a (about 1.5-fold) and the synthesis of extracellular carbohydrates (about 2-fold). At a high content of nitrate (20 mM) in the medium, when the growth of the parent strain and the synthesis of extracellular carbohydrates were inhibited, bactozole at all three concentrations exerted only a growth-stimulating effect. At the same time, mutant M-71 showed better growth at higher concentrations of bactozole, whereas the ability of the mutant to synthesize extracellular carbohydrates decreased with increasing bactozole concentration. The cell biomass of the mutant accumulated at 20 mM nitrate was 1.8–2.5 times greater than it was at 6 mM nitrate. Bactozole enhanced the symbiosis of legume plants with both parent and mutant strains, raising the mass of plants and enhancing nodulation and the nitrogen-fixing activity of root nodules. The symbiotic parameters of mutant M-71 were better (irrespective of whether bactozole was present or not) when its inoculum was grown at a high nitrogen content (20 mM nitrate), whereas the respective parameters of the parent strain were better when it was grown at 6 mM nitrate. The inference is made that the better physiological characteristics of the mutant in the high-nitrate medium are due to its higher nitrate reductase activity (as compared with the parent strain) in both the free-living state and in legume nodules.     

Effects of flow on the synthesis and release of fibronectin by endothelial cells

Summary Human umbilical vein endothelial cells at confluence were subjected to steady shear flow. The effect of flow on the synthesis of fibronectin, its release into the medium, and incorporation into the extracellular matrix were investigated. The total content of fibronectin in endothelial cells exposed to flow was found to be lower than that in static controls after periods of 12 to 48 h. In the presence of cycloheximide there was no difference in the fibronectin content of sheared and unsheared cells. Our results suggest that the synthesis of fibronectin is inhibited by the flow-induced perturbation of endothelial cells. This work was supported by grant EET 8708692 from the National Science Foundation, Washington, DC; grant HL-40696 from the National Institutes of Health, Bethesda, MD; and a Research Initiation Grant from the Pennsylvania State University.     

Purification of extracellular alkaline phosphatase released by Escherichia coli excretory mutants

Summary Alkaline phosphatase (APase) is the major protein released into the extracellular medium by strain 706, a periplasmic-excretory (lky) mutant of Escherichia coli K12. We developed a rapid three step procedure for APase purification from culture supernatants of lky mutants. Two ultrafiltration stages and an heat treatment were sufficient to obtain a 99% pure enzyme preparation. Batch culture conditions of strain 706 in a 15 l fermentor leading to an extracellular APase yield of 1250 U/ml were determined.Abbreviation APase E. coli alkaline phosphatase     

Effect of glucamylase on tissue glycogen and tissue glucamylase in the rat

1. A fungal glucamylase (alpha-1,4-glucan glucohydrolase, EC 3.2.1.3) from Aspergillus niger depresses liver glycogen stores after intraperitoneal injection into the rat. The injected enzyme rapidly disappears (within about 8hr.) from the serum; less than 1% is excreted in the urine, but it is rapidly taken up in the liver, spleen, kidney, cardiac and skeletal muscle. Elevated glucamylase concentrations could be demonstrated in liver and spleen tissues for 1-4 days after injection, but in kidney, cardiac and skeletal muscle elevated glucamylase concentrations could be shown only for periods of less than 24hr. after injection of the enzyme.     

The effects of various nutritional supplements on the growth,migration and differentiation ofxenopus laevis neural crest cells in vitro

Summary This study investigates the nutritional requirements ofXenopus laevis neural crest cells and melanophores developing in vitro. A comparison is made between the growth and differentiation of cells in serum-containing medium and a chemically defined, serum-free medium that we have designed. Our chemically defined medium is more efficient than serum-supplemented medium in promoting proliferation of these cells. Several supplements are required to enhance culture development. These include insulin, α-melanocyte stimulating hormone, somatotropin, luteotrophic hormone, linoleic acid, uridine, and putrescine. In addition, collagen and fibronectin provide the most conductive environment tested for cell migration and adhesion. This work was supported by establishment and major equipment grants from the Alberta Heritage Foundation for Medical Research to N. C. M. Nadine C. Milos is a Heritage Medical Research Scholar of the Alberta Heritage Foundation for Medical Research.     

Comparative studies on human skin fibroblasts: Life span and lipid metabolism in medium containing fetal bovine or human serum

Summary Three strains of human skin fibroblasts were cultivated in nutrient medium supplemented either with human serum or fetal bovine serum, and growth and lipid synthesis were compared. Rates of cellular growth were similar in both kinds of medium, but the replicative life spans of all three strains were curtailed significantly in human-serum medium. Incorporation of label into the major classes of neutral lipids from [¹⁴C]acetate and³H₂O was increased also in human-serum medium. Since human serum contained higher concentrations of cholesterol known to reduce endogenous cholesterol synthesis, these results were unexpected. Nonlipid factors in human serum may account for the shortened cellular life spans and increased lipogenesis and perhaps for the potential to develop atherosclerosis. Supported by grants from the Ontario Heart Foundation and Medical Research Council of Canada during the tenure of a Senior Research Fellowship from the Ontario Heart Foundation (J.T.C.) and a Scholarship from the Medical Research Council of Canada (S.G.).     

Mechanism of suppression inDrosophila: Regulation of tryptophan oxygenase by thesu(s) + allele

The suppressor gene,su(s)², inDrosophila melanogaster restores the production of red and brown eye pigments for some purple and vermilion mutant alleles, respectively. We showed previously that the product of thesu(s)⁺ allele caused inhibition of the sepiapterin synthase A produced by the purple mutant but did not affect the wild-type enzyme. Suppression was accomplished by removingsu(s)⁺ from the genome. We now report that the tryptophan oxygenase, produced by suppressible vermilion alleles, is also inhibited by extracts fromsu(s)⁺ flies. The inhibition of the vermilion enzyme can be reduced or eliminated, respectively, by prior storage of the extract at 4 or –20°C or by boiling, whereas the wild-type enzyme is not affected by extracts ofsu(s)⁺ flies. Also, when the suppressible vermilion strain is raised on certain diets, brown eye pigment production occurs. This epigenetic suppression was reduced by the presence of an extra copy ofsu(s)⁺ in the genome. These data support a posttranslational mechanism for regulation of enzyme activity in which the activity of the mutant enzyme is reduced by the product of thesu(s)⁺ allele. How thesu(s)⁺ gene product can distinguish between the normal and the mutant forms of these two enzymes is discussed, along with other mechanisms for suppression that are currently under investigation.This work was supported in part by a grant from the KOSEF, Korea Science and Engineering Foundation, and the National Science Foundation under the U.S.-East Asia Cooperative Science Program as well as the Office of Health and Environmental Research, U.S. Department of Energy, under Contract DE-AC05-840R21400 with the Martin Marietta Energy Systems, Inc.     

The production of protease by dense suspensions ofBacillus megaterium KM Sp−

The synthesis and secretion of extracellular protease was demonstrated during the incubation of dense susponsions of the asporogenicBacillus megaterium KM. The overall production of the enzyme by cells incubated with glucose in a nitrogen-free medium was found to be only slightly lower than that in the presence of an inorganic nitrogen source. The capacity to form protease decreased exponentially with increasing density of the bacterial suspension. The synthesis of the enzyme was interrupted after the exhaustion of glucose. A repeated exchange of the medium made it possible to reach relatively high and continuous production of protease for several hours. The total amount of extracellular proteins synthesized during incubation of the dense suspension in media with or without a nitrogen source was less than 2% of a total of newly formed proteins. The amount of these extracellular proteins was slightly lower in the absence of Ca²⁺ being considerably decreased when the dense suspension was incubated with chloramphenicol.     

野油菜黄单胞菌中3-羟基脂酰ACP脱水酶FabZ的生理功能

【背景】野油菜黄单胞菌(Xanthomonas campestris pv. campestris, Xcc)引起十字花科植物黑腐病,在全球范围内造成经济损失,亟须深入研究其致病机理,开发新的黑腐病防控措施。细菌脂肪酸合成系统不仅为细胞膜合成提供原料,其中间代谢产物还是许多生物活性分子合成的底物,具有重要的生理功能,也是抗菌药物筛选的重要靶标。【目的】研究XccfabZ对扩散信号分子(diffusible signal factor, DSF)类信号产量、致病力、胞外酶、胞外多糖和运动性等方面的影响。【方法】利用报告菌株检测法分析了不同替换突变株的DSF类群体感应信号产量。利用同源重组原理,在DSF类信号高产菌株中获得替换突变株,利用高效液相色谱(highperformanceliquid chromatography, HPLC)法测定DSF类信号产量。利用剪叶法检测替换突变株对寄主植物甘蓝的致病力,并分析了不同菌株的胞外多糖、胞外酶和运动性差异。【结果】报告菌株检测法和HPLC法都证明大肠杆菌fabZ替换突变株(XccΔfabZ/pSRK-EcfabZ)中DSF类信号产量显著下降。...     

A new RNA synthesis mutant of E. coli

A temperature-sensitive mutant of E. coli is described. At the nonpermissive temperature, the capacity for RNA and protein synthesis decreases logarithmically in the mutant. The mutant is unable to support the growth of f2 or T7 virus, even at the permissive temperature. The temperature-sensitive mutation maps approximately 1 away from rif ^r in E. coli and therefore affects a gene previously undescribed. The temperature sensitivity is suppressed by sublethal concentrations of rifampicin. Moreover, in rif ^r T^s double mutants, the T ^s mutation suppresses rif ^r and vice versa. The partially purified RNA polymerases from mutant and wild-type cells have different temperature and salt optima.This research was supported by Public Health Service grant GM-14368 from the National Institute of General Medical Sciences and by grant IN-29 from the American Cancer Society. One of us (D.P.) is a predoctoral trainee, supported by a National Science Foundation Graduate Traineeship Program and by a National Institutes of Health Predoctoral Research Fellowship. S. Marshall is supported by LASBAU.     

Characterization of a low-activity allele of NADP+-dependent isocitrate dehydrogenase from Drosophila melanogaster

We have characterized biochemical effects of Idh ^GB1 in Drosophila melanogaster. This is a null-activity allele for NADP⁺-dependent isocitrate dehydrogenase (NADP-IDH) isolated from a natural population. The homozygous mutant strain has 5% of the NADP-IDH specific activity found in controls and less than 24% of the immunologically cross-reacting material (CRM). This mutation maps to 27.2 on the third chromosome, to the right of h. The biochemical phenotype of this mutant strain includes a coordinate reduction in malic enzyme (ME) specific activity and CRM and an increase in specific activity for the pentose-phosphate shunt enzymes, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase. The K _m values for purified NADP-IDH are not different from those found for the purified control enzyme for NADP⁺ or isocitrate. It is suggested that this allele may represent a cis-acting control mutation for one of at least two loci involved in the production of NADP-IDH in D. melanogaster.Research supported by an Alberta Heritage Foundation for Medical Research Establishment Grant to MMB and a Natural Sciences and Engineering Research Council Operating Grant to JHW.     

Temperature-conditional nuclear mutation of Chlamydomonas reinhardtii decreases the CO2/O2 specificity of chloroplast ribulosebisphosphate carboxylase/oxygenase

The Chlamydomonas reinhardtii (Dangeard) temperature-conditional mutant 68-11AR is phenotypically indistinguishable from the wild type at the permissive temperature (25°C), but has greatly reduced photosynthetic ability and requires acetate for growth at the restrictive temperature (35°C). The mutant strain is deficient in ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) holoenzyme when grown at 35°C. This decrease in the level of enzyme appears to be due to degradation of assembled holoenzyme rather than to a reduction in the synthesis of enzyme subunits. When grown at 25°C, the mutant has a substantial amount of Rubisco. Enzyme purified from 25°C-grown mutant cells was found to have a 16% decrease in the CO₂/O₂ specificity factor when compared to the wild-type enzyme. This alteration was accompanied by changes in the kinetic constants for both carboxylation and oxygenation. Although the Rubisco active site is located on the chloroplast-encoded large subunit, genetic analysis showed that the 68-11AR strain arose from a nucleargene mutation. The two nuclear genes that encode the Rubisco small subunits (rbcS1 and rbcS2) were cloned from mutant 68-11AR and completely sequenced, but no mutation was found. Analysis of restriction-fragment length polymorphisms also failed to detect linkage between mutant and rbcS gene loci. These results indicate that nuclear genes can influence Rubisco catalysis without necessarily encoding polypeptides that reside within the holoenzyme.Abbreviations and Symbols K _c Michaelis constant for CO₂ - K _o Michaelis constant for O₂ - mt mating type - pf paralyzed flagella - RFLP restriction-fragment length polymorphism - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - RuBP ribulose 1,5-bisphosphate - V _c V _max for carboxylation - V _o V _max for oxygenation - CO₂/O₂ specificity factor C. G. gratefully acknowledges fellowship support from the Consejo Superior de Investigaciones Cientificas (Spain). This work was supported by National Science Foundation grant MCB-9005547, and is published as Paper No. 10481, Journal Series, Nebraska Agricultural Research Division.