Search results for "Cysteine"

Transmembrane beta-barrel of staphylococcal alpha-toxin forms in sensitive but not in resistant cells.

1997

Staphylococcal α-toxin is a 293-residue, single-chain polypeptide that spontaneously assembles into a heptameric pore in target cell membranes. To identify the pore-forming domain, substitution mutants have been produced in which single cysteine residues were introduced throughout the toxin molecule. By attaching the environmentally sensitive dye acrylodan to the sulfhydryl groups, the environment of individual amino acid side chains could be probed. In liposomes, a single 23-amino acid sequence (residues 118–140) was found to move from a polar to a nonpolar environment, indicating that this sequence forms the walls of the pore. However, periodicity in side chain environmental polarity coul…

Cysteine-Specific Radioiodination of Proteins with Fluorescein Maleimide

1997

A protocol is described for coupling of carrier-free iodine to protein sulfhydryl groups via fluorescein maleimide. 125I is first coupled to fluorescein maleimide in the presence of chloramine T. Iodination is stopped with sodium thiosulfate, and the iodine-substituted fluorescein maleimide is reacted with free cysteines of the protein. Excess label is then removed by gel-permeation chromatography. The procedure avoids exposition of the protein to oxidative conditions and does not require purification of the labeled carrier reagent. Suitability of the method for a given protein can be evaluated spectrophotometrically without employing radioactivity. It can be applied under denaturing condit…

2020

Mitochondrial fusion and fission tailors the mitochondrial shape to changes in cellular homeostasis. Players of this process are the mitofusins, which regulate fusion of the outer mitochondrial membrane, and the fission protein DRP1. Upon specific stimuli, DRP1 translocates to the mitochondria, where it interacts with its receptors FIS1, MFF, and MID49/51. Another fission factor of clinical relevance is GDAP1. Here, we identify and discuss cysteine residues of these proteins that are conserved in phylogenetically distant organisms and which represent potential sites of posttranslational redox modifications. We reveal that worms and flies possess only a single mitofusin, which in vertebrates…

Site-specific near-infrared fluorescent labelling of proteins on cysteine residues with meso -chloro-substituted heptamethine cyanine dyes

2018

International audience; Near-infrared (NIR) fluorescence imaging is a promising new medical imaging modality. Associated with a targeting molecule, NIR fluorophores can accumulate selectively in tissues of interest and become valuable tools for the diagnosis and therapy of various pathologies. To facilitate the design of targeted NIR imaging agents, it is important to identify simple and affordable fluorescent probes, allowing rapid labelling of biovectors such as proteins, ideally in a site-specific manner. Here, we demonstrate that heptamethine cyanine based fluorophores, such as IR-783, that contain a chloro-cyclohexyl moiety within their polymethine chain can react selectively, at neutr…

Site-Specific Dual Labeling of Proteins on Cysteine Residues with Chlorotetrazines

2018

International audience; Dual-labeled biomolecules constitute a new generation of bioconjugates with promising applications in therapy and diagnosis. Unfortunately, the development of these new families of biologics is hampered by the technical difficulties associated with their construction. In particular, the site specificity of the conjugation is critical as the number and position of payloads can have a dramatic impact on the pharmacokinetics of the bioconjugate. Herein, we introduce dichlorotetrazine as a trivalent platform for the selective double modification of proteins on cysteine residues. This strategy is applied to the dual labeling of albumin with a macrocyclic chelator for nucl…

Correlation between Low Folate Levels and Hyperhomocysteinemia, but not with Vitamin B12 in Hypertensive Patients.

2014

INTRODUCTION: Hypertension is considered to be among the most important risk factors for cardiovascular and cerebrovascular diseases. In recent years, several investigators have reported that high plasma levels of total homocysteine (t-hcy) has a key role in the development of hypertension, and the deficiency of B complex vitamins could increase the risk of hypertension. The purpose of this study was to investigate the relationship between plasma homocysteine, folate and vitamin B12 in hypertensive patients. MATERIALS AND METHODS: In 116 patients with hypertension and 81 healthy subjects, total plasma homocysteine, vitamin B12 and folate levels were measured. RESULTS AND DISCUSSION: Homocys…

Concentración plasmática de homocisteína: relación con los niveles plasmáticos de ácido fólico y con el polimorfismo 677C → T de la 5,10-metilenotetr…

2002

Antecedentes: El aumento moderado de la homocisteína plasmática en niños se ha relacionado con infartos cerebrales y trombosis venosas y con los antecedentes familiares de enfermedad coronaria prematura (ECP). La determinación de homocisteína en la infancia y el estudio de los factores que determinan su concentración podría ser importante para la prevención primaria de la ECP. Objetivo: Detectar algún caso de hiperhomocistinemia y valorar su relación con la concentración plasmática de ácido fólico y el polimorfismo 677C → T de la 5,10-metilenotetrahidrofolato reductasa (MTHFR). Métodos: Se ha estudiado mediante la regresión lineal múltiple la relación entre la concentración plasmática de ho…

Implications of cysteine metabolism in the heavy metal response in Trichoderma harzianum and in three Fusarium species

2009

We studied the ability of four different fungal species, Trichoderma harzianum, Fusarium antophyllum, Fusarium compactum and Fusarium phyllophilum, to grow in the presence of heavy metals, and monitored their cysteine and glutathione content and the activity of O-acetylserine(thiol)lyase (OASTL), which is involved in cysteine biosynthesis. Zn and Pb did not affect fungal growth or sporulation at the concentrations used, whereas Cd and Hg did. In most cases, cysteine and glutathione content was higher when fungi were grown in the presence of toxic metals. As T. harzianum and F. phyllophilum presented the best growth rate on Cd and Hg, they were selected to further analyse the accumulation of…

Apoptosis induced in hepatoblastoma HepG2 cells by the proteasome inhibitor MG132 is associated with hydrogen peroxide production, expression of Bcl-…

2002

This report is focused on the apoptotic effect induced by MG132, an inhibitor of 26S proteasome, in human hepatoma HepG2 cells. The results were compared with those obtained with non-transformed human Chang liver cells. MG132 reduced the viability of HepG2 cells in a time- and dose-dependent manner. The effect was in tight connection with the induction of apoptosis, as indicated by fluorescence microscopy and cytometric analysis, and was accompanied by a remarkable increase in the production of H2O2 and a reduction in mitochondrial transmembrane potential (Deltapsim). In addition cell death was prevented by antioxidants such as GSH, N-acetylcysteine or catalase. Western blot analysis showed…

Comparison of the chemopreventive efficacies of garlic powders with different alliin contents against aflatoxin B1 carcinogenicity in rats

2004

Garlic (Allium sativum) is well known for its beneficial effects on health and particularly for its chemopreventive potential against cancer. The present study was designed to compare the chemopreventive efficacies of several garlic powders with various levels of alliin, a precursor of active sulfur compounds. For this purpose we used the medium-term hepatocarcinogenesis protocol (resistant hepatocyte model), which allows the detection of preneoplasic foci expressing the placental form of glutathione S-transferase (GST-P) as an end-point. Rats were fed diets containing three garlic powders (5% of the diet) with various alliin contents for 3 weeks. Garlic powders were obtained from bulbs gro…