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1.
Dilip M. Shah Cathy M. Hironaka Roger C. Wiegand Elizabeth I. Harding Gwen G. Krivi David C. Tiemeier 《Plant molecular biology》1986,6(4):203-211
Summary We have used the cDNA clone encoding maize glutathione-S-transferase (GST I) to isolate a genomic DNA clone containing the complete GST I gene. Nucleotide sequence analysis of the cDNA and genomic clones has yielded a complete amino acid sequence for maize GST I and provided the exon-intron map of its gene. The mRNA homologous sequences in the maize GST I gene consist of a 107 bp 5 untranslated region, a 642 bp coding region and 340 bp of the 3 untranslated region. They are divided into three exons by two introns which interrupt the coding region. The 5 untranslated spacer contains an unusual sequence of pentamer AGAGG repeated seven times. The inbred maize line (Missouri 17) contains a single gene for GST I, whereas the hybrid line (3780A) contains two genes. Nucleotide sequence analysis of the primer extended cDNA products reveals that the 5 untranslated regions of the two genes in the hybrid 3780A are identical except for a 6 bp internal deletion (or insertion). The amino acid sequence of maize GST I shares no apparent sequence homology with the published sequences of animal GST's and represents the first published sequence of a plant GST. re]19850813 ac]19851126 相似文献
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Enzymic Dehalogenation of 4-Chlorobenzoyl Coenzyme A in Acinetobacter sp. Strain 4-CB1 总被引:2,自引:0,他引:2
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4-Chlorobenzoate degradation in cell extracts of Acinetobacter sp. strain 4-CB1 occurs by initial synthesis of 4-chlorobenzoyl coenzyme A (4-chlorobenzoyl CoA) from 4-chlorobenzoate, CoA, and ATP. 4-Chlorobenzoyl CoA is dehalogenated to 4-hydroxybenzoyl CoA. Following the dehalogenation reaction, 4-hydroxybenzoyl CoA is hydrolyzed to 4-hydroxybenzoate and CoA. Possible roles for the CoA moiety in the dehalogenation reaction are discussed. 相似文献
4.
Four different α-d-glucosyltransferases (GTF) have been obtained from culture filtrates of Streptococcus sobrinus strains grown in the chemostat at pH 6·5 in complex medium supplemented with Tween 80. Three of the enzymes, GTF-S1, GTF-S3 and GTF-S4, converted sucrose into soluble glucans. Their limit of hydrolysis with endodextranase, the proportion of linear to branched oligosaccharides among the end products of enzymic degradation, and methylation analysis, all supported the view that the glucans were dextrans. The S1-dextrans were highly branched (32% of α-(1 → 3)-branch points), S3-dextrans were linear, and the branching of S4-dextrans was intermediate in value (9%). The enzymes that catalyze the synthesis of three such diverse dextrans were thus proved to be three different GTF, each with a characteristic specificity. Conditions of growth in the chemostat could be varied to provide maximum yields of either GTF-S1, -S3 or -S4. 相似文献
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David O. Lambeth Gwen R. Ericson Mark A. Yorek Paul D. Ray 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,719(3):501-508
The influences of buffers and iron chelators on the rate of autoxidation of Fe2+ were examined in the pH range 6.0–7.4. The catalysis by Fe2+ and Fe3+ of the autoxidation of dithiothreitol was also investigated. In buffers which are non- or poor chelators of iron, 0.25 mM Fe2+, and 0.3 mM dithiothreitol when present with iron, oxidize within minutes at pH 7.4 and 30°C. The stability of each increases as the pH is decreased and more than 90% of each remains after 1 h at pH 6.0. In the presence of buffers or oxy-ligands which preferentially and strongly chelate Fe3+ over Fe2+, Fe2+ autoxidizes rapidly in the pH range 6.0–7.4 while dithiothreitol is protected. Ligands which preferentially bind strongly to Fe2+ stabilize both Fe2+ and dithiothreitol at pH 7.4. Dithiothreitol readily reduces Fe3+ in non-chelating buffers or in the presence of strong chelators of Fe2+, however, the ferrous ions produced are prone to reoxidation at higher pH values. These results show that Fe2+ and dithiothreitol are very susceptible to autoxidation in the neutral pH range, and that the rates are strongly influenced by the presence of chelators of Fe2+ and Fe3+. The rapid autoxidations of these species need to be taken into account when designing and interpreting experiments involving Fe2+ or both dithiothreitol and iron. 相似文献
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Sepiapterin synthase, the enzyme system responsible for the synthesis of sepiapterin from dihydroneopterin triphosphate, has been partially purified from extracts of the heads of young adult fruit flies (Drosophila melanogaster). The sepiapterin synthase system consists of two components, termed enzyme A (MW 82,000) and enzyme B (MW 36,000). Some of the properties of the enzyme system are as follows: NADPH and a divalent cation, supplied most effectively as MgCl2, are required for activity; optimal activity occurs at pH 7.4 and 30 C; the K
m
for dihydroneopterin triphosphate is 10 µm; and a number of unconjugated pterins, including biopterin and sepiapterin, are inhibitory. Dihydroneopterin cannot be used as substrate in place of dihydroneopterin triphosphate. Evidence is presented in support of a proposed reaction mechanism for the enzymatic conversion of dihydroneopterin triphosphate to sepiapterin in which enzyme A catalyzes the production of a labile intermediate by nonhydrolytic elimination of the phosphates of dihydroneopterin triphosphate, and enzyme B catalyzes the conversion of this intermediate, in the presence of NADPH, to sepiapterin. An analysis of the activity of sepiapterin synthase during development in Drosophila revealed the presence of a small amount of activity in eggs and young larvae and a much larger amount in late pupae and young adults. Sepiapterin synthase activity during development corresponds with the appearance of sepiapterin in the flies. Of a variety of eye color mutants of Drosophila melanogaster tested for sepiapterin synthase activity, only purple (pr) flies contained activity that was significantly lower than that found in the wild-type flies (22% of the wild-type activity). Further studies indicated that the amount of enzyme A activity is low in purple flies, whereas the amount of enzyme B activity is equal to that present in wild-type flies.This work was supported by research grants from the National Institutes of Health (AM03442) and the National Science Foundation (PCM75-19513 A02). G. G. K. was supported as a predoctoral trainee by National Institutes of Health Training Grant GM00515. 相似文献
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The Role of the Membrane-spanning Domain Sequence in Glycoprotein-mediated Membrane Fusion 总被引:1,自引:1,他引:1
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The role of glycoprotein membrane-spanning domains in the process of membrane fusion is poorly understood. It has been demonstrated that replacing all or part of the membrane-spanning domain of a viral fusion protein with sequences that encode signals for glycosylphosphatidylinositol linkage attachment abrogates membrane fusion activity. It has been suggested, however, that the actual amino acid sequence of the membrane-spanning domain is not critical for the activity of viral fusion proteins. We have examined the function of Moloney murine leukemia virus envelope proteins with substitutions in the membrane-spanning domain. Envelope proteins bearing substitutions for proline 617 are processed and incorporated into virus particles normally and bind to the viral receptor. However, they possess greatly reduced or undetectable capacities for the promotion of membrane fusion and infectious virus particle formation. Our results imply a direct role for the residues in the membrane-spanning domain of the murine leukemia virus envelope protein in membrane fusion and its regulation. They also support the thesis that membrane-spanning domains possess a sequence-dependent function in other protein-mediated membrane fusion events. 相似文献
10.
Lana Sargent Mike Nalls Andrew Singleton Priya Palta Anna Kucharska-Newton Jim Pankow Hunter Young Weihong Tang Pamela Lutsey Amy Olex Jered M. Wendte Danni Li Alvaro Alonso Michael Griswold B. Gwen Windham Stefania Baninelli Luigi Ferrucci 《Aging cell》2024,23(2):e14030
Aging adults experience increased health vulnerability and compromised abilities to cope with stressors, which are the clinical manifestations of frailty. Frailty is complex, and efforts to identify biomarkers to detect frailty and pre-frailty in the clinical setting are rarely reproduced across cohorts. We developed a predictive model incorporating biological and clinical frailty measures to identify robust biomarkers across data sets. Data were from two large cohorts of older adults: “Invecchiare in Chianti (Aging in Chianti, InCHIANTI Study”) (n = 1453) from two small towns in Tuscany, Italy, and replicated in the Atherosclerosis Risk in Communities Study (ARIC) (n = 6508) from four U.S. communities. A complex systems approach to biomarker selection with a tree-boosting machine learning (ML) technique for supervised learning analysis was used to examine biomarker population differences across both datasets. Our approach compared predictors with robust, pre-frail, and frail participants and examined the ability to detect frailty status by race. Unique biomarker features identified in the InCHIANTI study allowed us to predict frailty with a model accuracy of 0.72 (95% confidence interval (CI) 0.66–0.80). Replication models in ARIC maintained a model accuracy of 0.64 (95% CI 0.66–0.72). Frail and pre-frail Black participant models maintained a lower model accuracy. The predictive panel of biomarkers identified in this study may improve the ability to detect frailty as a complex aging syndrome in the clinical setting. We propose several concrete next steps to keep research moving toward detecting frailty with biomarker-based detection methods. 相似文献