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891.
David M. Byers Harold W. Cook Frederick B. St. C. Palmer Matthew W. Spence 《Neurochemical research》1989,14(6):503-509
Distinct sets of cellular proteins were labeled with [3H]myristic and [3H]palmitic acids in primary (rat neurons and astroglia) and continuous (murine N1E-115 neuroblastoma and rat C6 glioma) cell cultures derived from the nervous system. Both soluble and membrane proteins were modified by myristate in a hydroxylamine-stable (amide) linkage, while palmitoylated proteins were esterlinked and almost exclusively membrane bound. Chain elongation of both labeled fatty acids prior to acylation was observed, but no protein amide-liked [3H]myristate originating from [3H]palmitate was detected. Fatty acylation profiles differed considerably among most of the cell lines, except for rat astroglial and glioma cells in which myristoylated proteins appeared to be almost identical based on SDS gel electrophoresis. An unidentified 47 kDa myristoylated protein was labeled to a significantly greater extent in astroglial than in glioma cells; the expression of this protein could be related to transformation or development in cells of glial origin. 相似文献
892.
The previous demonstration that incubation of brain slices with [32P]phosphate brings about rapid tabeling of phosphatidic acid in myelin suggests that the enzyme involved should be present in this specialized membrane. DAG kinase (ATP:1,2-diacyglycerol 3-phosphotransferase, E.C. 2.7.1.107) is present in rat brain homogenate at a specific activity of 2.5 nmol phosphatidic acid formed/min/mg protein, while highly purified myelin had a much lower specific activity (0.29 nmol/min/mg protein). Nevertheless, the enzyme appears to be intrinsic to this membrane since it can not be removed by washing with a variety of detergents or chelating agents, and it could not be accounted for as contamination by another subcellular fraction. Production of endogenous, membrane-associated, diacylglycerol (DAG) by PLC (phospholipase C) treatment brought about translocation from soluble to particulate fractions, including myelin. Another level of control of activity involves inactivation by phosphorylation; a 10 min incubation of brain homogenate with ATP resulted in a large decrease in DAG kinase activity in soluble, particulate and myelin fractions. 相似文献
893.
Eubacterial isocitrate dehydrogenase with dual specificity for NAD and NADP from Rhodomicrobium vannielii 总被引:1,自引:0,他引:1
Abstract Cell-free extracts of the photosynthetic eubacterium Rhodomicrobium vannielii contained both NADP and NAD-linked isocitrate dehydrogenase activities. Apparent K m values of 12 μM for NADP, 0.75 mM for NAD, 9.3 μM for isocitrate (NADP utilising) and 8.2 μM for isocitrate (NAD utilising) were determined in such extracts. Four lines of evidence indicated that one enzyme was responsible for the two activities; (i) non-additivity of reaction rates in the presence of both NADP and NAD (ii) the presence of one band which stained for activity with both cofactors on non-denaturing polyacrylamide gels (iii) identical heat inactivation kinetics for both activities (iv) co-elution of both activities after ion-exchange and hydrophobic interaction chromatography. This is the first report of a eubacterial isocitrate dehydrogenase with dual cofactor specificity. 相似文献
894.
Lisa R. Williamson Gregory V. Piano Herbert H. Winkler Duncan C. Krause David O. Wood 《Gene》1989,80(2):269-278
The Rickettsia prowazekii ATP/ADP translocase (Tlc) gene (tlc), previously cloned in Escherichia coli was localized to a 1.6-kb chromosomal fragment. Nucleotide sequence analysis of this fragment revealed an open reading frame of 1494 bp that could encode a hydrophobic protein of 497 amino acids (aa) with an Mr of 56 668. Analysis of the deduced aa sequence revealed that it contained twelve potential membrane-spanning regions. Comparisons between the deduced aa sequence of the R. prowazekii ATP/ADP Tlc and the sequences of mitochondrial (mt) Tic revealed no detectable homologies between the rickettsial and mt sequences. The major protein synthesized in E. coli minicells containing the rickettsial gene exhibited an Mr of approx. 34000. 相似文献
895.
Validation of signature polarlipid fatty acid biomarkers for alkane-utilizing bacteria in soils and subsurface aquifer materials 总被引:3,自引:0,他引:3
David B. Ringelberg John D. Davis Glen A. Smith Susan M. Pfiffner Peter D. Nichols Janet S. Nickels J.Michael Henson John T. Wilson Marylynn Yates Donald H. Kampbell Harvey W. Read Thomas T. Stocksdale David C. White 《FEMS microbiology letters》1989,62(1):39-50
Abstract Extractable cell membrane-derived polarlipid ester-linked fatty acids (PLFA) obtained from aerated soils gassed with methane or propane and from methane- and propane-oxidizing bacteria isolated from the soils were analyzed by capillary gas chromatography/mass spectrometry. Exposure of aerated soils to methane resulted in the formation of a high proportion of an unusual 18-carbon mono-unsaturated PLFA, 18:lw8c. High proportions of this fatty acid biomarker are found in monocultures from this soil grown in minimal media with methane. This PLFA has been previously established as associated with authentic type II methane-oxidizing bacteria. The microbiota in aerated soils exposed to hydrocarbons containing propane, formed a suite of PLFA characterized by high proportions of a 16-carbon mono-unsaturated acid, 16:lw6c, and an 18-carbon saturated fatty acid with an additional methyl branch at the 10 position, 10 Me 18:0. This PLFA pattern has been detected in several monocultures enriched from the soil with propane-amended minimal media. The correspondence of high proportions of these unusual mono-unsaturated PLFA in the isolated monocultures and in situ in the soils after stimulation with the appropriate hydrocarbon is a strong validation of the utility of these biomarkers in defining the community structure of the surface soil microbial community. 相似文献
896.
The construction and use of two novel transposon(Tn)-delivery vectors is described. These vectors carry Inc.W or Inc.N broad-host-range transfer functions cloned next to the narrow-host-range replicon of pBR329. The host specificities of pSLX10 and pSLX23 both complement and extend the host specificities of existing Tn delivery vectors. Plasmids pSLX10 and pSLX23 were shown to transfer at high frequency in intergeneric matings. The lux genes which are present on each vector permit the visual monitoring of transconjugants which have retained a Tn element, but are devoid of plasmid molecules. pSLX10 and pLSX23 were efficiently used to generate a range of auxotrophic mutants in various strains of Pseudomonas as well as to clone genes from Serratia liquefaciens. These vectors may have general applicability to identify and clone genes in a wide range of Gram-negative bacteria. 相似文献
897.
David G. Mann 《Plant Systematics and Evolution》1989,163(1-2):43-52
Amphiraphia
Chen & Zhu, together with theAmphiraphiaceae andAmphiraphidales, should be abandoned, sinceAmphiraphia cells are the heterovalvar initial cells ofCaloneis. WhenCaloneis reproduces sexually two cells pair and become surrounded by a two-layered capsule of mucilage. Each cell produces two gametes and these become rearranged within the gametangial frustule before plasmogamy. The gametes are amoeboid and fusion is isogamous. Following plasmogamy the zygote contracts, becomes ellipsoidal, and lays down a primary perizonial band. This is a complete, wide hoop, while subsequent perizonial bands are narrow and open. 相似文献
898.
The evolution of the Australian flora through the Tertiary has not been reviewed by a megafossil palaeobotanist for almost a century. Based on material available and published studies, the Australian Tertiary can be considered in three units: Eocene, Oligo-Miocene, and Pliocene. Key taxa in the Eocene includeCasuarinaceae, Proteaceae, Fagaceae, Podocarpaceae, andLauraceae. Many known Eocene deposits are interpreted as warm, humid rainforests.Oligo-Miocene floras reflect a climatic deterioration, with greater occurrence of sclerophylly and xerophylly. A reduction of tropical taxa is seen with an increase ofMyrtaceae and earliest records ofMimosaceae, Chenopodiaceae, andPoaceae. These trends continue into the Pliocene, which is not well represented in Australia.Problems needing to be addressed include the discrepancy between the pollen and megafossil records ofNothofagus, the origins of Australia's wet tropical taxa, and the role of fire in the early evolution of the Australian flora. 相似文献
899.
David W. Fujino David W. Burger Kent J. Bradford 《Journal of Plant Growth Regulation》1989,8(1):53-61
Five-day-old, dark-grown seedlings of theEpinastic (Epi) tomato mutant (Lycopersicon esculentum Mill.) and its parent, cultivar VFN8, were used as a system for assessing the role of ethylene in theEpi phenotype. The distinguishing features ofEpi seedlings are an increase in hypocotyl diameter and reduced hypocotyl length. Treatment of VFN8 seedlings with 0.5 l/liter ethylene closely mimicked theEpi phenotype. The rate of ethylene production by 5-day-old, dark-grownEpi seedlings was double that of VFN8 seedlings. Nevertheless, treatment ofEpi seedlings with inhibitors of ethylene biosynthesis (aminoethoxyvinylglycine or Co2+) or ethylene action (silver thiosulfate or norbornadiene) failed to normalize theEpi phenotype.Epi seedlings grown in sealed jars containing ethylene and CO2 adsorbants also expressed the characteristicEpi phenotype. The results indicate that the physiological lesion resulting from theEpi gene mutation is not simply an overproduction of ethylene. 相似文献
900.
A group of 14 9-substituted derivatives of 6-benzylaminopurine (BA), including the alanine conjugate, oxygen heterocyclic
and alkyl derivatives, and compounds with a modified 9-ribose moiety, were assessed for their ability to retard soybean leaf
senescence. The 9-alanine conjugate was very weakly active, and only two compounds, 9-(2-tetrahydropyranyl)-BA (9THP-BA) and
9-(2-tetrahydrofuranyl)-BA (9THF-BA), proved to be considerably more effective than BA. The metabolism of these three BA derivatives
was determined to rationalize their differing activity. The alanine conjugate of BA was largely unmetabolized in leaf discs,
but 9THP-BA and 9THF-BA released free BA and were also debenzylated to 9THP-adenine and 9THF-adenine, respectively. The three
products of metabolism were identified by mass spectrometry. The enhanced activity of 9THP-BA and 9THF-BA, relative to that
of BA, is attributed to their greater stability and their ability to gradually release free BA. This released BA was less
susceptible to inactivation by alanine conjugate formation than was exogenous BA. The novel BA analogue 7-benzylaminooxazolo[5,4-d]pyrimidine,
in which the 9-NH is replaced by oxygen, was inactive at 100 μM.
For part II, see Zhang et al. 1987 相似文献