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"Michael, Anthony J."
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Functional polyamine metabolic enzymes and pathways encoded by the virosphere
Viruses produce more viruses by manipulating the metabolic and replication systems of their host cells. Many have acquired metabolic genes from ancestral hosts and use the encoded enzymes to subvert host metabolism. The polyamine spermidine is required for bacteriophage and eukaryotic virus replication, and herein, we have identified and functionally characterized diverse phage- and virus-encoded polyamine metabolic enzymes and pathways. These include pyridoxal 5′-phosphate (PLP)-dependent ornithine decarboxylase (ODC), pyruvoyl-dependent ODC and arginine decarboxylase (ADC), arginase, S-adenosylmethionine decarboxylase (AdoMetDC/speD), spermidine synthase, homospermidine synthase, spermidine N-acetyltransferase, and N-acetylspermidine amidohydrolase. We identified homologs of the spermidine-modified translation factor eIF5a encoded by giant viruses of the Imitervirales. Although AdoMetDC/speD is prevalent among marine phages, some homologs have lost AdoMetDC activity and have evolved into pyruvoyl-dependent ADC or ODC. The pelagiphages that encode the pyruvoyl-dependent ADCs infect the abundant ocean bacterium Candidatus Pelagibacter ubique, which we have found encodes a PLP-dependent ODC homolog that has evolved into an ADC, indicating that infected cells would contain both PLP- and pyruvoyldependent ADCs. Complete or partial spermidine or homospermidine biosynthetic pathways are found encoded in the giant viruses of the Algavirales and Imitervirales, and in addition, some viruses of the Imitervirales can release spermidine from the inactive N-acetylspermidine. In contrast, diverse phages encode spermidine N-acetyltransferase that can sequester spermidine into its inactive N-acetyl form. Together, the virome-encoded enzymes and pathways for biosynthesis and release or biochemical sequestration of spermidine or its structural analog homospermidine consolidate and expand evidence supporting an important and global role of spermidine in virus biology.
Journal Article
Policy agendas in British politics
\"Through a unique dataset covering half a century of policy-making in Britain, this book traces how topics like the economy, international affairs, and crime have changed in their importance to government. The data concerns key venues of decision-making - the Queen's Speech, laws and budgets - which are compared to the media and public opinion. These trends are conveyed through accessible figures backed up by a series of examples of important policies. As a result, the book throws new light on the key points of change in British politics, such as Thatcherism and New Labour and explores different approaches to agenda setting helping to account for these changes: incrementalism, the issue attention cycle and the punctuated equilibrium model. What results is the development of a new approach to agenda setting labelled focused adaptation whereby policy-makers respond to structural shifts in the underlying pattern of attention\"-- Provided by publisher.
Book
Polyamine Oxidase5 Regulates Arabidopsis Growth through Thermospermine Oxidase Activity
The major plant polyamines (PAs) are the tetraamines spermine (Spm) and thermospermine (T-Spm), the triamine spermidine, and the diamine putrescine. PA homeostasis is governed by the balance between biosynthesis and catabolism; the latter is catalyzed by polyamine oxidase (PAO). Arabidopsis (Arabidopsis thaliana) has five PAO genes, AtPAOl to AtPAO5, and all encoded proteins have been biochemically characterized. All AtPAO enzymes function in the back-conversion of tetraamine to triamine and/or triamine to diamine, albeit with different PA specificities. Here, we demonstrate that AtPAO5 loss-of-function mutants (pao5) contain 2-fold higher T-Spm levels and exhibit delayed transition from vegetative to reproductive growth compared with that of wild-type plants. Although the wild type and pao5 are indistinguishable at the early seedling stage, externally supplied low-dose T-Spm, but not other PAs, inhibits aerial growth of pao5 mutants in a dose-dependent manner. Introduction of wild-type AtPAOS into pao5 mutants rescues growth and reduces the T-Spm content, demonstrating that AtPAO5 is a T-Spm oxidase. Recombinant AtPAO5 catalyzes the conversion of T-Spm and Spm to triamine spermidine in vitro. AtPAO5 specificity for T-Spm in planta may be explained by coexpression with T-Spm synthase but not with Spm synthase. The pao5 mutant lacking T-Spm oxidation and the acl5 mutant lacking T-Spm synthesis both exhibit growth defects. This study indicates a crucial role for T-Spm in plant growth and development.
Journal Article
الاقتصاد
إن كتاب (الاقتصاد) لـ (بول آ. سامويلسون، ويليام د. نوردهاوس، مايكل ج. ماندل) هو كتاب أساسي ومرجع هام جدا في الإقتصاد يتكون الكتاب من (791) صفحة تقريبا من القطع الكبير المزدوج، تم التصوير بالألوان بسبب وجود رسومات توضيحية يتكون من 37 فصل .. يبدأ الفصل الأول بأسس علم الاقتصاد وينتهي الفصل السابع والثلاثون بإدارة الاقتصاد العالمي مرورا بالمدارس الاقتصادية.
BOOK
The buck stops with spermidine
Sirtuins remove post-translationally added acyl groups from protein lysines. New work shows the surprising metabolic fate of acyl groups removed from mitochondrial proteins—they react nonenzymatically with essential polyamine spermidine, forming previously unknown monoacylated
N
-glutarylspermidines and diacylated
N
-glutaryl,
N
-acetylspermidines.
Journal Article
Novel Polyamine Acyltransferase Responsible for the Accumulation of Spermidine Conjugates in Arabidopsis Seed
Hydroxycinnamic acid amides are a class of secondary metabolites distributed widely in plants. We have identified two sinapoyl spermidine derivatives, N-((4'-O-glycosyl)-sinapoyl),N'-sinapoylspermidine and N,N'-disinapoylspermidine, which comprise the two major polyamine conjugates that accumulate in Arabidopsis thaliana seed. Using metabolic profiling of knockout mutants to elucidate the functions of members of the BAHD acyltransferase family in Arabidopsis, we have also identified two genes encoding spermidine disinapoyl transferase (SDT) and spermidine dicoumaroyl transferase (SCT) activities. At2g23510, which is expressed mainly in seeds, encodes a spermidine sinapoyl CoA acyltransferase (SDT) that is required for the production of disinapoyl spermidine and its glucoside in Arabidopsis seed. The structurally related BAHD enzyme encoded by At2g25150 is expressed specifically in roots and has spermidine coumaroyl CoA acyltransferase (SCT) activity both in vitro and in vivo.
Journal Article
Spermine synthase
Spermine is present in many organisms including animals, plants, some fungi, some archaea, and some bacteria. It is synthesized by spermine synthase, a highly specific aminopropyltransferase. This review describes spermine synthase structure, genetics, and function. Structural and biochemical studies reveal that human spermine synthase is an obligate dimer. Each monomer contains a C-terminal domain where the active site is located, a central linking domain that also forms the lid of the catalytic domain, and an N-terminal domain that is structurally very similar to
S
-adenosylmethionine decarboxylase. Gyro mice, which have an X-chromosomal deletion including the spermine synthase (
SMS
) gene, lack all spermine and have a greatly reduced size, sterility, deafness, neurological abnormalities, and a tendency to sudden death. Mutations in the human
SMS
lead to a rise in spermidine and reduction of spermine causing Snyder-Robinson syndrome, an X-linked recessive condition characterized by mental retardation, skeletal defects, hypotonia, and movement disorders.
Journal Article
Engineering plants with increased levels of the antioxidant chlorogenic acid
The trend to view many foods not only as sustenance but also as medicine, so-called functional foods, is increasing. Phenolics are the most widespread dietary antioxidants, and among these, chlorogenic acid (CGA) accumulates to high levels in some crop plants. CGA acts as an antioxidant in plants and protects against degenerative, age-related diseases in animals when supplied in their diet. cDNA clones encoding the enzyme that synthesizes CGA, hydroxycinnamoyl-CoA quinate: hydroxycinnamoyl transferase (HQT), were characterized from tomato and tobacco. Gene silencing proved HQT to be the principal route for accumulation of CGA in solanaceous species. Overexpression of HQT in tomato caused plants to accumulate higher levels of CGA, with no side-effects on the levels of other soluble phenolics, and to show improved antioxidant capacity and resistance to infection by a bacterial pathogen. Tomatoes with elevated CGA levels could be used in foods with specific benefits for human health.
Journal Article