124 research outputs found
Nanofiltration of a Landfill Leachate Containing Pharmaceutical Intermediates from Vitamin C Production
The main landfill of the city of Zagreb generates several hundreds of cubic meters of heavily contaminated leachate per day. The organic composition of the leachate is particularly peculiar because, besides common macromolecular humus-like dissolved organic carbon,it encompasses a number of specific compounds of pharmaceutical origin, including a suite of by-products deriving from the production of vitamin C. Since both macromolecular humic organic matter and vitamin C intermediates are rather resistant to microbial degradation, leachate treatment procedures using simple retention lagoons or conventional bioreactors are not very effective in reducing their levels before the discharge into the receiving waters. An attractive alternative is the application of membrane technology. The efficiencies of three different types of nanofilters for the purification of leachates from the Jakuševec landfill were examined. It was shown that both complex humic-like dissolved organic matter and anthropogenic compounds of pharmaceutical origin can be eliminated at high efficiencies, mostly above 90 %
Structure and mechanism of a canonical poly(ADP-ribose) glycohydrolase
Poly(ADP-ribosyl)ation is a reversible post-translational protein modification involved in the regulation of a number of cellular processes including DNA repair, chromatin structure, mitosis, transcription, checkpoint activation, apoptosis and asexual development. The reversion of poly(ADP-ribosyl)ation is catalysed by poly(ADP-ribose) (PAR) glycohydrolase (PARG), which specifically targets the unique PAR (1''-2') ribose-ribose bonds. Here we report the structure and mechanism of the first canonical PARG from the protozoan Tetrahymena thermophila. In addition, we reveal the structure of T. thermophila PARG in a complex with a novel rhodanine-containing mammalian PARG inhibitor RBPI-3. Our data demonstrate that the protozoan PARG represents a good model for human PARG and is therefore likely to prove useful in guiding structure-based discovery of new classes of PARG inhibitors
Family-wide analysis of poly(ADP-ribose) polymerase activity
The poly(adenosine diphosphate (ADP)-ribose) polymerase (PARP) protein family generates ADP-ribose (ADPr) modifications onto target proteins using NAD[superscript +] as substrate. Based on the composition of three NAD[superscript +] coordinating amino acids, the H-Y-E motif, each PARP is predicted to generate either poly(ADPr) (PAR) or mono(ADPr) (MAR). However, the reaction product of each PARP has not been clearly defined, and is an important priority since PAR and MAR function via distinct mechanisms. Here we show that the majority of PARPs generate MAR, not PAR, and demonstrate that the H-Y-E motif is not the sole indicator of PARP activity. We identify automodification sites on seven PARPs, and demonstrate that MAR and PAR generating PARPs modify similar amino acids, suggesting that the sequence and structural constraints limiting PARPs to MAR synthesis do not limit their ability to modify canonical amino-acid targets. In addition, we identify cysteine as a novel amino-acid target for ADP-ribosylation on PARPs.Rita Allen FoundationSidney Kimmel FoundationNational Cancer Institute (U.S.) (Cancer Center Support (Core) Grant P30-CA14051)National Institutes of Health (U.S.) (Grant RO1GM087465)Kathy and Curt Marble Cancer Research FundWellcome Trust (London, England)European Research Counci
Chemical Composition and Physical Properties of “Pale Yellow” Naphtalan
The Pale Yellow (PY) Naphthalan is potentially a new treatment modality for some oral mucosal
and dermatological diseases. Its chemical composition and physical properties were studied by standard
and sophisticated methods. Special attention was paid to steranes and hopanes as favorable components
and to aromatics as unfavorable compounds. PY Naphthalan is predominantly composed of saturated aliphatic
hydrocarbons of different structures, and of hydrocarbons comprising aromatic ring(s) (< 15%).
Among aromatics, 98% were monoaromatics and 2% diaromatics, while 16 polycyclic aromatic hydrocarbons
designated by US Environmental Protection Agency as priority pollutants were found at minimum
detectability levels. Steranes and hopanes appeared in native geogenic clusters of homologs and
each of identified compounds was in native geogenic configuration. Steranes were in the range from norcholestanes
up to propyl cholestanes and hopanes up to pentakishomohopanes. The content of steranes
and hopanes was relatively high. Compared to the other naphthalan products, the composition of PY
Naphthalan is remarkably improved. Physical properties make PY Naphthalan convenient for application.
(doi: 10.5562/cca1886
Visualization of poly(ADP-ribose) bound to PARG reveals inherent balance between exo- and endo-glycohydrolase activities
Poly-ADP-ribosylation is a post-translational modification that regulates processes involved in genome stability. Breakdown of the poly(ADP-ribose) (PAR) polymer is catalysed by poly(ADP-ribose) glycohydrolase (PARG), whose endo-glycohydrolase activity generates PAR fragments. Here we present the crystal structure of PARG incorporating the PAR substrate. The two terminal ADP-ribose units of the polymeric substrate are bound in exo-mode. Biochemical and modelling studies reveal that PARG acts predominantly as an exo-glycohydrolase. This preference is linked to Phe902 (human numbering), which is responsible for low-affinity binding of the substrate in endo-mode. Our data reveal the mechanism of poly-ADP-ribosylation reversal, with ADP-ribose as the dominant product, and suggest that the release of apoptotic PAR fragments occurs at unusual PAR/PARG ratios
Actions of aprataxin in multiple DNA repair pathways
Mutations in the Aptx gene lead to a neurological disorder known as ataxia oculomotor apraxia-1. The product of Aptx is Aprataxin (Aptx), a DNA-binding protein that resolves abortive DNA ligation intermediates. Aprataxin catalyzes the nucleophilic release of adenylate groups covalently linked to 5' phosphate termini, resulting in termini that can again serve as substrates for DNA ligases. Here we show that Aprataxin acts preferentially on adenylated nicks and double-strand breaks rather than on single-stranded DNA. Moreover, we show that whereas the catalytic activity of Aptx resides within the HIT domain, the C-terminal zinc finger domain provides stabilizing contacts that lock the enzyme onto its high affinity AMP-DNA target site. Both domains are therefore required for efficient AMP-DNA hydrolase activity. Additionally, we find a role for Aprataxin in base excision repair, specifically in the removal of adenylates that arise from abortive ligation reactions that take place at incised abasic sites in DNA. We suggest that Aprataxin may have a general proofreading function in DNA repair, removing DNA adenylates as they arise during single-strand break repair, double-strand break repair, and in base excision repair
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