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Dependent Methyltransferase (dependent + methyltransferase)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

3-Methylarginine from Pseudomonas syringae pv. syringae 22d/93 Suppresses the Bacterial Blight Caused by Its Close Relative Pseudomonas syringae pv. glycinea

CHEMBIOCHEM, Issue 12 2008
Sascha D. Braun
Abstract The epiphyte Pseudomonas syringae pv. syringae 22d/93 (Pss22d) produces a toxin that strongly inhibits the growth of its relative, the plant pathogen P. syringae pv. glycinea. The inhibition can be overcome by supplementing the growth medium with the essential amino acid, L -arginine; this suggests that the toxin acts as an inhibitor of the arginine biosynthesis. The highly polar toxin was purified by bioassay-guided fractionation using ion-exchange chromatography and subsequent RP-HPLC fractionation. The structure of the natural product was identified by HR-ESI-MS, HR-ESI-MS/MS, and NMR spectroscopy experiments as 3-methylarginine. This amino acid has previously only been known in nature as a constituent of the peptide lavendomycin from Streptomyces lavendulae. Results of experiments in which labeled methionine was fed to Pss22d indicated that the key step in the biosynthesis of 3-methylarginine is the introduction of the methyl group by a S -adenosylmethionine (SAM)-dependent methyltransferase. Transposon mutagenesis of Pss22d allowed the responsible SAM-dependent methyltransferase of the 3-methylarginine biosynthesis to be identified. [source]

Myxovirescin A Biosynthesis is Directed by Hybrid Polyketide Synthases/Nonribosomal Peptide Synthetase, 3-Hydroxy-3-Methylglutaryl,CoA Synthases, and trans-Acting Acyltransferases

CHEMBIOCHEM, Issue 8 2006
Vesna Simunovic M.S.
Abstract Myxococcus xanthus DK1622 is shown to be a producer of myxovirescin (antibiotic TA) antibiotics. The myxovirescin biosynthetic gene cluster spans at least 21 open reading frames (ORFs) and covers a chromosomal region of approximately 83 kb. In silico analysis of myxovirescin ORFs in conjunction with genetic studies suggests the involvement of four type I polyketide synthases (PKSs; TaI, TaL, TaO, and TaP), one major hybrid PKS/NRPS (Ta-1), and a number of monofunctional enzymes similar to the ones involved in type II fatty-acid biosyntesis (FAB). Whereas deletion of either taI or taL causes a dramatic drop in myxovirescin production, deletion of both genes (,taIL) leads to the complete loss of myxovirescin production. These results suggest that both TaI and TaL PKSs might act in conjunction with a methyltransferase, reductases, and a monooxygenase to produce the 2-hydroxyvaleryl,S,ACP starter that is proposed to act as the biosynthetic primer in the initial condensation reaction with glycine. Polymerization of the remaining 11 acetates required for lactone formation is directed by 12 modules of Ta-1, TaO, and TaP megasynthetases. All modules, except for the first module of TaL, lack cognate acyltransferase (AT) domains. Furthermore, deletion of a discrete tandem AT,encoded by taV,blocks myxovirescin production; this suggests an "in trans" mode of action. To embellish the macrocycle with methyl and ethyl moieties, assembly of the myxovirescin scaffold is proposed to switch twice from PKS to 3-hydroxy-3-methylglutaryl,CoA (HMG,CoA)-like biochemistry during biosynthesis. Disruption of the S -adenosylmethionine (SAM)-dependent methyltransferase, TaQ, shifts production toward two novel myxovirescin analogues, designated myxovirescin Qa and myxovirescin Qc. NMR analysis of purified myxovirescin Qa revealed the loss of the methoxy carbon atom. This novel analogue lacks bioactivity against E. coli. [source]

Structure of a class II TrmH tRNA-modifying enzyme from Aquifex aeolicus

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2005
Elizabeth Pleshe
Biological RNAs contain a variety of post-transcriptional modifications that facilitate their efficient function in the cellular environment. One of the two most common forms of modification is methylation of the 2,-hydroxyl group of the ribose sugar, which is performed by a number of S -adenosylmethionine (SAM) dependent methyltransferases. In bacteria, many of these modifications in tRNA and rRNA are carried out by the ,/,-knot superfamily of enzymes, whose SAM-binding pocket is created by a characteristic deep trefoil knot. TrmH, an enzyme found throughout all three kingdoms of life, modifies the universally conserved guanosine 18 position of tRNA. The crystal structure of TrmH from the thermophilic bacterium Aquifex aeolicus has been determined at 1.85,Å resolution using data collected from a synchrotron-radiation source. The protein reveals a fold typical of members of the SpoU clan of proteins, a subfamily of the ,/,-knot superfamily, with ,-helical extensions at the N- and C-termini that are likely to be involved in tRNA binding. [source]

Synthesis of S -Adenosyl- L -homocysteine Capture Compounds for Selective Photoinduced Isolation of Methyltransferases

CHEMBIOCHEM, Issue 2 2010
Christian Dalhoff Dr.
Abstract Understanding the interplay of different cellular proteins and their substrates is of major interest in the postgenomic era. For this purpose, selective isolation and identification of proteins from complex biological samples is necessary and targeted isolation of enzyme families is a challenging task. Over the last years, methods like activity-based protein profiling (ABPP) and capture compound mass spectrometry (CCMS) have been developed to reduce the complexity of the proteome by means of protein function in contrast to standard approaches, which utilize differences in physical properties for protein separation. To isolate and identify the subproteome consisting of S -adenosyl- L -methionine (SAM or AdoMet)-dependent methyltransferases (methylome), we developed and synthesized trifunctional capture compounds containing the chemically stable cofactor product S -adenosyl- L -homocysteine (SAH or AdoHcy) as selectivity function. SAH analogues with amino linkers at the N6 or C8 positions were synthesized and attached to scaffolds containing different photocrosslinking groups for covalent protein modification and biotin for affinity isolation. The utility of these SAH capture compounds for selective photoinduced protein isolation is demonstrated for various methyltransferases (MTases) acting on DNA, RNA and proteins as well as with Escherichia coli cell lysate. In addition, they can be used to determine dissociation constants for MTase,cofactor complexes. [source]