Occurrence of histone-related oxalate binding in rat liver nucleus

The rat liver nuclear oxalate binding protein was isolated, purified by anion and cation exchange column chromatography using Diethyl Amino Ethyl Sephadex, Carboxy Methyl Cellulose and Carboxy Methyl Sephadex C-50 ion exchangers. The purified oxalate binding protein was found to be H1B of H1 fraction of histories. Kinetic analysis of oxalate binding showed the presence of two affinity sites, one with Kd of 133.5 nM and Bmax of 40 pmoles and another with Kd of 262.5 nM and Bmax of 210 pmoles. The optimal oxalate binding was at pH 4.2 and at 28°C. The oxalate binding was specific and reversible and not due to ionic charge interaction. The IC₅₀ of other dicarboxylates was higher than that of oxalate. EGTA had no effect on oxalate binding but di- and tri-carboxylate carrier inhibitors and thiol modifying agents significantly lowered the binding activity. Oxalate binding to histones was significantly reduced in the presence of DNA or nucleotides, but RNA had no effect. ATP completely inhibited the oxalate binding activity at 1 mM concentration. Different tissues exhibited oxalate binding showing ubiquitous nature. Calf thymus H1 showed maximal binding similar to liver histones.Abbreviations ADP Adenosine diphosphate - ATP Adenosine triphosphate - DNA Deoxyribonucleic acid - RNA Ribonucleic acid     

Impact of chronic sub-lethal methylparaben exposure on cardiac hypoxia and alterations in neuroendocrine factors in zebrafish model

Molecular Biology Reports - Endocrine-disrupting chemicals have been shown to cause toxicity in different systems of the body including the endocrine, cardiovascular and nervous systems. This study...     

Sequential Anterograde and Retrograde Conduction Block during Radiofrequency Ablation of an Accessory Pathway

We present an interesting image showing sequential loss of anterograde, and subsequently, retrograde conduction during radiofrequency ablation of an accessory pathway. We discuss the possible mechanisms and prior literature concerning this interesting finding.     

Functional mapping of community‐acquired respiratory distress syndrome (CARDS) toxin of Mycoplasma pneumoniae defines regions with ADP‐ribosyltransferase,vacuolating and receptor‐binding activities

Community‐acquired respiratory distress syndrome (CARDS) toxin from Mycoplasma pneumoniae is a 591‐amino‐acid virulence factor with ADP‐ribosyltransferase (ADPRT) and vacuolating activities. It is expressed at low levels during in vitro growth and at high levels during colonization of the lung. Exposure of experimental animals to purified recombinant CARDS toxin alone is sufficient to recapitulate the cytopathology and inflammatory responses associated with M. pneumoniae infection in humans and animals. Here, by molecular modelling, serial truncations and site‐directed mutagenesis, we show that the N‐terminal region is essential for ADP‐ribosylating activity. Also, by systematic truncation and limited proteolysis experiments we identified a portion of the C‐terminal region that mediates toxin binding to mammalian cell surfaces and subsequent internalization. In addition, the C‐terminal region alone induces vacuolization in a manner similar to full‐length toxin. Together, these data suggest that CARDS toxin has a unique architecture with functionally separable N‐terminal and C‐terminal domains.