Purification of a GSH-affinity binding protein from Bacteroides fragilis devoid of glutathione transferase activity

For the location of the aminoglycoside-(3)-N-acetyltransferase isoenzyme II (AAC(3)-II) in the bacterial cell, two strains were studied: Escherichia coli HB101(pJV03), producing the 31-kDa AAC (3)-II enzyme, and E. coli HB101, which served as a control. From each strain five protein fractions were prepared: culture supernatant, and proteins occurring in the periplasm, cytoplasm, inner membrane and outer membrane. All fractions were tested for enzymatic activity of AAC(3)-II. Most of the acetylating activity was found in the cytoplasmic fraction. The distribution of marker enzymes showed a good separation between the periplasmic and the cytoplasmic fraction.     

Left ventricular noncompaction cardiomyopathy

Isolated left ventricular noncompaction (ILVNC) is a congenital abnormality in the structure of ventricular tissue due to amorphogenetic defect during embryogenesis. This rare entity can be easily diagnosed by the characteristic appearance of prominent trabeculations and deep inter-trabecular spaces. Clinical manifestations of this disease include benign and malignant ventricular arrhythmia, congestive heart failure signs, cardio-embolic events (stroke), mitral and pulmonary valve incompetence, and reduced global ventricular systolic function. We present the case report of a 58-year-old man with ILVNC.     

Molecular basis underlying the biological effects elicited by extremely low-frequency magnetic field (ELF-MF) on neuroblastoma cells

Extremely low-frequency magnetic fields (ELF-MFs) may affect human health because of the possible associations with leukemia but also with cancer, cardiovascular, and neurological disorders. In the present work, human SH-SY5Y neuroblastoma cells were exposed to a 50 Hz, 1 mT sinusoidal ELF-MF at three different times, that is, 5 days (T5), 10 days (T10), and 15 days (T15) and then the effects of ELF-MF on proteome expression and biological behavior were investigated. Through comparative analysis between treated and control samples, we analyzed the proteome changes induced by ELF-MF exposure. Nine new proteins resolved in sample after a 15-day treatment were involved in a cellular defense mechanism and/or in cellular organization and proliferation such as peroxiredoxin isoenzymes (2, 3, and 6), 3-mercaptopyruvate sulfurtransferase, actin cytoplasmatic 2, t-complex protein subunit beta, ropporin-1A, and profilin-2 and spindlin-1. Our results indicated that ELF-MFs exposure altered the proliferative status and other important cell biology-related parameters, such as cell growth pattern, and cytoskeletal organization. These findings support our hypothesis that ELF radiation could trigger a shift toward a more invasive phenotype.     

Phenotypic profile linked to inhibition of the major Zn influx system in Salmonella enterica: proteomics and ionomics investigations

Zinc is required for a wide variety of cellular functions and plays a key role in bacterial metabolism and virulence. However, Zn can also be toxic and, therefore, its influx is tightly regulated. The high affinity zinc uptake transporter ZnuABC is the main Zn influx system in Salmonella enterica under conditions of Zn starvation. It has been shown that deletion of the gene encoding for its periplasmic subunit ZnuA significantly affects S. Typhimurium growth rate and virulence, highlighting the importance of this system in the host-pathogen interaction. To gain further insight into the mechanisms involved in Zn influx regulation, we characterized the main alterations in the ionome and proteome of S. Typhimurium wild type and znuA mutant strains grown either under Zn starvation or under Zn-replete conditions. We found significant differences in the element profile and protein expression that were reversed by Zn supplementation. In particular, several of the differentially regulated proteins are predicted to be metal-binding proteins. Interestingly, their over-expression in the znuA mutant strain strictly depends on Zn starvation and correlates with the differences found at the ionome level. In conclusion, our data demonstrate that inhibition of Zn influx has relevant effects either on the bacterial ionome or proteome and shed new light on the role of the ZnuABC system and Zn influx in S. Typhimurium pathogenicity.     

A conserved hydrogen-bond network stabilizes the structure of Beta class glutathione S-transferases

We identified a network of hydrogen bonds that is conserved in the structures of bacterial Beta class glutathione S-transferases (GSTs). It is formed by three residues: a serine, a histidine and a glutamate, together with a water molecule that links the serine with the histidine. This network connects the first helix of the N-terminal glutaredoxin-like domain with the last helix of the C-terminal GST-specific all helical domain. Here we show that substitution of Ochrobactrum anthropi GST His15 and Glu198 with alanine greatly compromises the catalytic efficiency of the enzyme, even though none of these residues takes part to the enzyme active site. Thermal and chemical denaturation experiments point to a role for this network in global structure stabilization. Furthermore, we show that OaGST structure looses compactness at alkanine pHs and that this behavior may be ascribed to partial disruption of the H-bond network, pointing to an important role in zippering the N-terminal and C-terminal domains of the protein.     

Morphofunctional mitochondrial response to methylglyoxal toxicity in Bufo bufo embryos

Methylglyoxal (2-oxopropanal) is a reactive alpha-oxoaldehyde that can be formed endogenously mainly as a by-product of glycolytic pathway. It is a cytotoxic compound with significant antiproliferative properties as it can bind, under physiological conditions, to nucleic acids and proteins, forming stable adducts. We have recently shown that exogenous methylglyoxal (150-600 microM) is highly toxic for amphibian embryos where it produces, when added to the culture water, inhibition of cell proliferation in the early developmental stages, followed by severe malformations and strongly reduced embryonic viability. In this work we investigate the morphofunctional effect of methylglyoxal on the common toad B. bufo embryo mitochondria in order to verify if its dysmorphogenetic action might be also ascribed to impairment of mitochondrial functions. The mitochondria were isolated from embryos at the developmental stages of morula, neural plate and operculum complete and developing in the presence of 600 microM methylglyoxal. The results show that exogenous methylglyoxal is highly toxic at mitochondrial level, where it produces proliferation, swelling and membrane derangement. As a consequence, mitochondria from treated embryos show decreased oxidative phosphorylation efficiency, as indicated by the significant reduction both of the respiratory control index values and of the embryonic ATP content. On the basis of these data, it is possible that the methylglyoxal-induced embryonic malformations as well as the strongly reduced viability might be also ascribed to energy depletion.     

A quantitative method for the analysis of glycated and glutathionylated hemoglobin by matrix-assisted laser desorption ionization-time of flight mass spectrometry

The quantization of glycated isoforms of hemoglobin has been increasingly used in clinical practice in recent years. Glycated hemoglobin is currently considered the most important measurement for long-term control of the glycemic state and it has become a reference tool for the management of diabetes. Glutathionylated hemoglobin is an increasingly clinically relevant covalent adduct of glutathione with beta chain of the globin and its concentration has been correlated with oxidative stress. We have developed an innovative technique based on linear mode matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry for quantitative analysis of hemoglobin species. This method was applied to the quantification of glycated and glutathionylated hemoglobin. A rigorous comparison was pursued to evaluate the analytical performances in quantifying glycated hemoglobin in comparison to an established high-performance liquid chromatography method. Our results indicated a complete equivalence between the two methods. The same analysis enabled the quantitative determination of the glutathionylated hemoglobin fraction. This isoform was investigated in an adult Italian population (184 individuals, 101 males and 83 females), indicating a bimodal distribution of this species. In fact 65.22% of screened individuals had glutathionylated hemoglobin levels lower than 0.50% while 34.78% had glutathionylated hemoglobin levels higher than 0.50%. A semiautomatic robotic procedure was developed for fast analysis of a large number of samples. This is the first report of a quantitative application of linear MALDI-TOF mass spectrometry for the determination of glutathionylated hemoglobin in blood samples. This method allows fast screening of this hemoglobin isoform, therefore opening the route to explore its specificity and sensitivity as a molecular biomarker.     

Properties and utility of the peculiar mixed disulfide in the bacterial glutathione transferase B1-1

Bacterial glutathione transferases appear to represent an evolutionary link between the thiol:disulfide oxidoreductase and glutathione transferase superfamilies. In particular, the observation of a mixed disulfide in the active site of Proteus mirabilis glutathione transferase B1-1 is a feature that links the two families. This peculiar mixed disulfide between Cys10 and one GSH molecule has been studied by means of ESR spectroscopy, stopped-flow kinetic analysis, radiochemistry, and site-directed mutagenesis. This disulfide can be reduced by dithiothreitol but even a thousand molar excess of GSH is poorly effective due to an unfavorable equilibrium constant of the redox reaction (K(eq) = 2 x 10(-4)). Although Cys10 is partially buried in the crystal structure, in solution it reacts with several thiol reagents at a higher or comparable rate than that shown by the free cysteine. Kinetics of the reaction of Cys10 with 4,4'-dithiodipyridine at variable pH values is consistent with a pK(a) of 8.0 +/- 0.1 for this residue, a value about 1 unit lower than that of the free cysteine. The 4,4'-dithiodipyridine-modified enzyme reacts with GSH in a two-step mechanism involving a fast precomplex formation, followed by a slower chemical step. The natural Cys10-GSH mixed disulfide exchanges rapidly with free [3H]GSH in a futile redox cycle in which the bound GSH is continuously replaced by the external GSH. Our data suggest that the active site of the bacterial enzyme has intermediate properties between those of the recently evolved glutathione transferases and those of the thiol:disulfide oxidoreductase superfamily.