Search results for "methionine"

Adaptive antioxidant methionine accumulation in respiratory chain complexes explains the use of a deviant genetic code in mitochondria

2008

Humans and most other animals use 2 different genetic codes to translate their hereditary information: the standard code for nuclear-encoded proteins and a modern variant of this code in mitochondria. Despite the pivotal role of the genetic code for cell biology, the functional significance of the deviant mitochondrial code has remained enigmatic since its first description in 1979. Here, we show that profound and functionally beneficial alterations on the encoded protein level were causative for the AUA codon reassignment from isoleucine to methionine observed in most mitochondrial lineages. We demonstrate that this codon reassignment leads to a massive accumulation of the easily oxidized …

Catalysis in glycine N-methyltransferase: testing the electrostatic stabilization and compression hypothesis.

2006

Glycine N-methyltransferase (GNMT) is an S-adenosyl-l-methionine dependent enzyme that catalyzes glycine transformation to sarcosine. Here, we present a hybrid quantum mechanics/molecular mechanics (QM/MM) computational study of the reaction compared to the counterpart process in water. The process takes place through an SN2 mechanism in both media with a transition state in which the transferring methyl group is placed in between the donor (SAM) and the acceptor (the amine group of glycine). Comparative analysis of structural, electrostatic, and electronic characteristics of the in-solution and enzymatic transition states allows us to get a deeper insight into the origins of the enzyme's c…

Expanding the chemical scope of RNA:methyltransferases to site-specific alkynylation of RNA for click labeling.

2010

This work identifies the combination of enzymatic transfer and click labeling as an efficient method for the site-specific tagging of RNA molecules for biophysical studies. A double-activated analog of the ubiquitous co-substrate S-adenosyl-l-methionine was employed to enzymatically transfer a five carbon chain containing a terminal alkynyl moiety onto RNA. The tRNA:methyltransferase Trm1 transferred the extended alkynyl moiety to its natural target, the N2 of guanosine 26 in tRNA(Phe). LC/MS and LC/MS/MS techniques were used to detect and characterize the modified nucleoside as well as its cycloaddition product with a fluorescent azide. The latter resulted from a labeling reaction via Cu(I…

Homocysteine and S-adenosylated metabolites in cardiovascular disease

2010

A major unanswered question is whether direct cellular toxicity of homocysteine (Hcy) is causally involved in cardiovascular disease (CVD) in humans or whether homocysteinemia is simply a passive and indirect indicator of a more complex mechanism. Alternatively or additionally, the association between Hcy and CVD may result from its metabolic precursor S-adenosyl-Hcy (SAH), or from the altered ratio of S-adenosylmethionine SAM/SAH. This competition is based on the known effects of these adenosylated metabolites on cellular methylation, disturbances of which may lead to endothelial dysfunction and/ or CVD. Thus, it is of great significance to know how these adenosylated metabolites (SAM, SAH…

Effect of metabolic promoters on yeld and fruit quality of 'Sanfilippara' and 'Trabia' loquat.

2014

CCDC 742171: Experimental Crystal Structure Determination

2009

Related Article: C.H.Gorbitz, K.Rissanen, A.Valkonen, A.Husabo|2009|Acta Crystallogr.,Sect.C:Cryst.Struct.Commun.|65|o267|doi:10.1107/S0108270109014309

CCDC 2128259: Experimental Crystal Structure Determination

2022

Related Article: Mariafrancesca Baratta, Teresa Fina Mastropietro, Rosaria Bruno, Antonio Tursi, Cristina Negro, Jesús Ferrando-Soria, Alexander I. Mashin, Aleksey Nezhdanov, Fiore P. Nicoletta, Giovanni De Filpo, Emilio Pardo, Donatella Armentano|2022|ACS Appl. Nano Mater.|5|5223|doi:10.1021/acsanm.2c00280

Crystallization and preliminary X-ray analysis of native and selenomethionyl vinorine synthase from Rauvolfia serpentina.

2005

Vinorine synthase (VS) is a central enzyme of the biosynthesis of the antiarrhythmic drug ajmaline and is a member of the BAHD superfamily of acyltransferases. So far, no three-dimensional structure with significant sequence homology with VS is known. Crystals of VS and selenomethionyl-labelled VS from the medicinal plant Rauvolfia serpentina have been obtained by the hanging-drop technique at 305 K with ammonium sulfate and PEG 400 as precipitants. VS crystals diffract to 2.8 Å and belong to space group P212121, with unit-cell parameters a = 82.3, b = 89.6, c = 136.2 Å. The selenomethionyl VS crystal was nearly isomorphous with the VS crystal.

Robustness of PET Radiomics Features: Impact of Co-Registration with MRI

2021

Radiomics holds great promise in the field of cancer management. However, the clinical application of radiomics has been hampered by uncertainty about the robustness of the features extracted from the images. Previous studies have reported that radiomics features are sensitive to changes in voxel size resampling and interpolation, image perturbation, or slice thickness. This study aims to observe the variability of positron emission tomography (PET) radiomics features under the impact of co-registration with magnetic resonance imaging (MRI) using the difference percentage coefficient, and the Spearman’s correlation coefficient for three groups of images: (i) original PET, (ii) PET after co-…

Differential effects of cysteine and methionine residues in the antioxidant activity of human serum albumin

2005

Antioxidant properties of human serum albumin (HSA) may explain part of its beneficial role in various diseases related to free radical attack. In the present study, the antioxidant role of Cys and Met was studied by copper-mediated oxidation of human low density lipoproteins and by free radical-induced blood hemolysis which essentially assessed metal-chelating and free radical scavenging activities, respectively. Mild conditions were set up to specifically modify Cys and Met residues by N-ethylmaleimide (NEM) and chloramine T treatments, respectively. We found that Met and Cys accounted for 40-80% of total antioxidant activity of HSA. Copper binding to HSA was decreased by about 50% with c…