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https://www.readbyqxmd.com/read/28191919/lysine-tryptophan-crosslinked-peptides-produced-by-radical-sam-enzymes-in-pathogenic-streptococci
#1
Kelsey R Schramma, Mohammad R Seyedsayamdost
Macrocycles represent a common structural framework in many naturally-occurring peptides. Several strategies exist for macrocyclization, and the corresponding enzymes are of great interest, as they enhance our repertoire for creating complex molecules. We recently discovered a new peptide cyclization reaction involving a crosslink between the side-chains of lysine and tryptophan that is installed by a radical SAM enzyme. Herein, we characterize relatives of this metalloenzyme from the pathogens Streptococcus agalactiae and Streptococcus suis...
February 13, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/28164386/a-class-c-radical-s-adenosylmethionine-methyltransferase-synthesizes-8-methylmenaquinone
#2
Sascha Hein, Oliver Klimmek, Markus Polly, Melanie Kern, Jörg Simon
The membranous quinone/quinol pool is essential to the majority of life forms and has been widely used as an important biomarker in microbial taxonomy. In the anaerobic world, the most important quinones are menaquinone (MK) and a methylated form of MK, designated methylmenaquinone (MMK), which is anticipated to serve specifically in low-potential electron transport chains involved in anaerobic respiration. However, it has remained unclear how MMK is generated. Here we show that a novel enzyme homologous to class C radical SAM methyltransferases (RSMTs) synthesizes MMK using MK as substrate...
February 6, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28112859/the-catalytic-mechanism-of-the-class-c-radical-s-adenosylmethionine-methyltransferase-nosn
#3
Wei Ding, Yongzhen Li, Junfeng Zhao, Xinjian Ji, Tianlu Mo, Haocheng Qianzhu, Tao Tu, Zixin Deng, Yi Yu, Fener Chen, Qi Zhang
S-Adenosylmethionine (SAM) is one of the most common co-substrates in enzyme-catalyzed methylation reactions. Most SAM-dependent reactions proceed through an SN 2 mechanism, whereas a subset of them involves radical intermediates for methylating non-nucleophilic substrates. Herein, we report the characterization and mechanistic investigation of NosN, a class C radical SAM methyltransferase involved in the biosynthesis of the thiopeptide antibiotic nosiheptide. We show that, in contrast to all known SAM-dependent methyltransferases, NosN does not produce S-adenosylhomocysteine (SAH) as a co-product...
January 23, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28108243/tpx2-as-a-prognostic-indicator-and-potential-therapeutic-target-in-clear-cell-renal-cell-carcinoma
#4
Zachary A Glaser, Harold D Love, Shunhua Guo, Lan Gellert, Sam S Chang, Stanley Duke Herrell, Daniel A Barocas, David F Penson, Michael S Cookson, Peter E Clark
OBJECTIVES: Our aims were to determine if targeting protein for Xklp2 (TPX2) is correlated with clear cell renal cell carcinoma (ccRCC) histology and oncologic outcomes using The Cancer Genome Atlas (TCGA) and an institutional tissue microarray (TMA). METHODS: Clinicopathological data obtained from the TCGA consisted of 415 samples diagnosed with ccRCC. A TMA was constructed from tumors of 207 patients who underwent radical nephrectomy for ccRCC. TPX2 expression by immunohistochemistry on TMA was assessed by a genitourinary pathologist...
January 17, 2017: Urologic Oncology
https://www.readbyqxmd.com/read/28093141/re-utility-and-significance-of-ureteric-frozen-section-analysis-during-radical-cystectomy
#5
Sam S Chang
No abstract text is available yet for this article.
February 2017: Journal of Urology
https://www.readbyqxmd.com/read/28067841/lectin-digestibility-and-stability-of-elderberry-antioxidants-to-heat-treatment-in-vitro
#6
Pilar Jiménez, Patricia Cabrero, Damian Cordoba-Diaz, Manuel Cordoba-Diaz, Manuel Garrosa, Tomás Girbés
Elderberry contains healthy low molecular weight nutraceuticals and lectins which are sequence-related to the elderberry allergen Sam n1. Some of these lectins are type II ribosome-inactivating proteins. The sensitivity of native lectins present in elderberry fruits and bark to the proteolysis triggered by in vitro simulated gastric and duodenal fluids has been investigated. It was found that these lectins are refractory to proteolysis. Nonetheless, incubation for 5-10 min in a boiling water bath completely sensitized them to the hydrolytic enzymes in vitro...
January 6, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28047832/su-d-bra-06-duodenal-interfraction-motion-with-abdominal-compression
#7
A Witztum, D Holyoake, S Warren, M Partridge, M Hawkins
PURPOSE: To quantify the effect of abdominal compression on duodenal motion during pancreatic radiotherapy. METHODS: Seven patients treated for pancreatic cancer were selected for analysis. Four patients were treated with abdominal compression and three without. The duodenum was contoured by the same physician on each CBCT (five CBCTs for patients with compression, four for non-compression patients). CBCTs were rigidly registered using a soft tissue match and contours were copied to the delivered plans which were all radical (BED > 50 Gy)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28045519/7-carboxy-7-deazaguanine-synthase-a-radical-s-adenosyl-l-methionine-enzyme-with-polar-tendencies
#8
Nathan A Bruender, Tsehai A J Grell, Daniel P Dowling, Reid M McCarty, Catherine L Drennan, Vahe Bandarian
Radical S-adenosyl-l-methionine (SAM) enzymes are widely distributed and catalyze diverse reactions. SAM binds to the unique iron atom of a site-differentiated [4Fe-4S] cluster and is reductively cleaved to generate a 5'-deoxyadenosyl radical, which initiates turnover. 7-Carboxy-7-deazaguanine (CDG) synthase (QueE) catalyzes a key step in the biosynthesis of 7-deazapurine containing natural products. 6-Carboxypterin (6-CP), an oxidized analogue of the natural substrate 6-carboxy-5,6,7,8-tetrahydropterin (CPH4), is shown to be an alternate substrate for CDG synthase...
February 8, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28045510/anaerobic-heme-degradation-chuy-is-an-anaerobilin-reductase-that-exhibits-kinetic-cooperativity
#9
Joseph W LaMattina, Michael Delrossi, Katherine G Uy, Nicholas D Keul, David B Nix, Anudeep R Neelam, William N Lanzilotta
Heme catabolism is an important biochemical process that many bacterial pathogens utilize to acquire iron. However, tetrapyrrole catabolites can be reactive and often require further processing for transport out of the cell or conversion to another useful cofactor. In previous work, we presented in vitro evidence of an anaerobic heme degradation pathway in Escherichia coli O157:H7. Consistent with reactions that have been reported for other radical S-adenosyl-l-methionine methyltransferases, ChuW transfers a methyl group to heme by a radical-mediated mechanism and catalyzes the β-scission of the porphyrin macrocycle...
January 26, 2017: Biochemistry
https://www.readbyqxmd.com/read/28040895/biosynthesis-of-branched-alkoxy-groups-iterative-methyl-group-alkylation-by-a-cobalamin-dependent-radical-sam-enzyme
#10
Yuanyou Wang, Bastien Schnell, Sascha Baumann, Rolf Müller, Tadhg P Begley
The biosynthesis of branched alkoxy groups, such as the unique t-butyl group found in a variety of natural products, is still poorly understood. Recently, cystobactamids were isolated and identified from Cystobacter sp as novel antibacterials. These metabolites contain an isopropyl group proposed to be formed using CysS, a cobalamin-dependent radical S-adenosylmethionine (SAM) methyltransferase. Here, we reconstitute the CysS-catalyzed reaction, on p-aminobenzoate thioester substrates, and demonstrate that it not only catalyzes sequential methylations of a methyl group to form ethyl and isopropyl groups but remarkably also sec-butyl and t-butyl groups...
January 25, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28027411/dna-repair-by-the-radical-sam-enzyme-spore-photoproduct-lyase-from-biochemistry-to-structural-investigations
#11
REVIEW
Olivier Berteau, Alhosna Benjdia
Radical S-adenosyl-L-methionine (SAM) enzymes have emerged as one of the last superfamilies of enzymes discovered to date. Arguably, it is the most versatile group of enzymes involved in at least 85 biochemical transformations. One of the founding members of this enzyme superfamily is the spore photoproduct (SP) lyase, a DNA repair enzyme catalyzing the direct reversal repair of a unique DNA lesion, the so-called spore photoproduct, back into two thymidine residues. Discovered more than 20 years ago in the bacterium Bacillus subtilis, SP lyase has been shown to be widespread in the endospore-forming Firmicutes from the Bacilli and Clostridia classes and to use radical-based chemistry to perform C-C bond breakage, a chemically challenging reaction...
December 27, 2016: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/27998091/tryptophan-lyase-nosl-a-cornucopia-of-5-deoxyadenosyl-radical-mediated-transformations
#12
Dhananjay M Bhandari, Dmytro Fedoseyenko, Tadhg P Begley
Tryptophan lyase (NosL) is a radical S-adenosyl-l-methionine (SAM) enzyme that catalyzes the formation of 3-methyl-2-indolic acid from l-tryptophan. In this paper, we demonstrate that the 5'-deoxyadenosyl radical is considerably more versatile in its chemistry than previously anticipated: hydrogen atom abstraction from Nα-cyclopropyltryptophan occurs at Cα rather than the amino group with NosL Y90A and replacing the substrate amine with a ketone or an alkene changes the chemistry from hydrogen atom abstraction to double bond addition...
December 21, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27994052/bcid-is-a-radical-s-adenosyl-l-methionine-sam-enzyme-that-completes-bacteriochlorophyllide-e-biosynthesis-by-oxidizing-a-methyl-group-into-a-formyl-group-at-c-7
#13
Jennifer L Thweatt, Bryan H Ferlez, John H Golbeck, Donald A Bryant
Green bacteria are chlorophotorophs that synthesize bacteriochlorophyll (BChl) c, d, or e, which assemble into supramolecular, nanotubular structures in large light-harvesting structures called chlorosomes. The biosynthetic pathways of these chlorophylls are known except for one reaction. Null mutants of bciD, which encodes a putative radical S-adenosyl-l-methionine (SAM) protein, are unable to synthesize BChl e but accumulate BChl c; however, it is unknown whether BciD is sufficient to convert BChl c (or its precursor, bacteriochlorophyllide (BChlide) c) into BChl e (or BChlide e)...
January 27, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/27979570/re-the-effect-of-broader-directed-antimicrobial-prophylaxis-including-fungal-coverage-on-perioperative-infectious-complications-after-radical-cystectomy
#14
https://www.readbyqxmd.com/read/27936626/oxidative-cyclization-in-natural-product-biosynthesis
#15
Man-Cheng Tang, Yi Zou, Kenji Watanabe, Christopher T Walsh, Yi Tang
Oxidative cyclizations are important transformations that occur widely during natural product biosynthesis. The transformations from acyclic precursors to cyclized products can afford morphed scaffolds, structural rigidity, and biological activities. Some of the most dramatic structural alterations in natural product biosynthesis occur through oxidative cyclization. In this Review, we examine the different strategies used by nature to create new intra(inter)molecular bonds via redox chemistry. This Review will cover both oxidation- and reduction-enabled cyclization mechanisms, with an emphasis on the former...
December 12, 2016: Chemical Reviews
https://www.readbyqxmd.com/read/27934015/the-b12-radical-sam-enzyme-poyc-catalyzes-valine-c%C3%AE-methylation-during-polytheonamide-biosynthesis
#16
Aubérie Parent, Alain Guillot, Alhosna Benjdia, Gwladys Chartier, Jérôme Leprince, Olivier Berteau
Genomic and metagenomic investigations have recently led to the delineation of a novel class of natural products called ribosomally synthesized and post-translationally modified peptides (RiPPs). RiPPs are ubiquitous among living organisms and include pharmaceutically relevant compounds such as antibiotics and toxins. A prominent example is polytheonamide A, which exhibits numerous post-translational modifications, some of which were unknown in ribosomal peptides until recently. Among these post-translational modifications, C-methylations have been proposed to be catalyzed by two putative radical S-adenosylmethionine (rSAM) enzymes, PoyB and PoyC...
December 7, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27929146/reactivity-of-the-nitrogen-centered-tryptophanyl-radical-in-the-catalysis-by-the-radical-sam-enzyme-nosl
#17
Haocheng Qianzhu, Wenjuan Ji, Xinjian Ji, Leixia Chu, Chuchu Guo, Wei Lu, Wei Ding, Jiangtao Gao, Qi Zhang
The radical SAM tryptophan (Trp) lyase NosL involved in nosiheptide biosynthesis catalyzes two parallel reactions, converting l-Trp to 3-methyl-2-indolic acid (MIA) and to dehydroglycine and 3-methylindole, respectively. The two parallel reactions diverge from a nitrogen-centered tryptophanyl radical intermediate. Here we report an investigation on the intrinsic reactivity of the tryptophanyl radical using a chemical model study and DFT calculations. The kinetics of the formation and fragmentation of this nitrogen-centered radical in NosL catalysis were also studied in detail...
December 22, 2016: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/27902775/determinants-of-trna-recognition-by-the-radical-sam-enzyme-rlmn
#18
Christina M Fitzsimmons, Danica Galonić Fujimori
RlmN, a bacterial radical SAM methylating enzyme, has the unusual ability to modify two distinct types of RNA: 23S rRNA and tRNA. In rRNA, RlmN installs a methyl group at the C2 position of A2503 of 23S rRNA, while in tRNA the modification occurs at nucleotide A37, immediately adjacent to the anticodon triplet. Intriguingly, only a subset of tRNAs that contain an adenosine at position 37 are substrates for RlmN, suggesting that the enzyme carefully probes the highly conserved tRNA fold and sequence features to identify its targets...
2016: PloS One
https://www.readbyqxmd.com/read/27859789/radical-reaction-control-in-the-adomet-radical-enzyme-cdg-synthase-quee-consolidate-destabilize-accelerate
#19
Christof M Jäger, Anna K Croft
Controlling radical intermediates and thus catalysing and directing complex radical reactions is a central feature of S-adensosylmethionine (SAM)-dependent radical enzymes. We report ab initio and DFT calculations highlighting the specific influence of ion complexation, including Mg(2+) , identified as a key catalytic component on radical stability and reaction control in 7-carboxy-7-deazaguanine synthase (QueE). Radical stabilisation energies (RSEs) of key intermediates and radical clock-like model systems of the enzyme-catalysed rearrangement of 6-carboxytetrahydropterin (CPH4), reveals a directing role of Mg(2+) in destabilising both the substrate-derived radical and corresponding side reactions, with the effect that the experimentally-observed rearrangement becomes dominant over possible alternatives...
November 10, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27834682/does-viperin-function-as-a-radical-s-adenosyl-l-methionine-dependent-enzyme-in-regulating-farnesylpyrophosphate-synthase-expression-and-activity
#20
Caitlyn Makins, Soumi Ghosh, Gabriel D Román-Meléndez, Paige A Malec, Robert T Kennedy, E Neil G Marsh
Viperin is an endoplasmic reticulum-associated antiviral responsive protein that is highly up-regulated in eukaryotic cells upon viral infection through both interferon-dependent and independent pathways. Viperin is predicted to be a radical S-adenosyl-l-methionine (SAM) enzyme, but it is unknown whether viperin actually exploits radical SAM chemistry to exert its antiviral activity. We have investigated the interaction of viperin with its most firmly established cellular target, farnesyl pyrophosphate synthase (FPPS)...
December 23, 2016: Journal of Biological Chemistry
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