In Vitro Study on Structural Alteration of Myoglobin by Methylglyoxal

Methylglyoxal (MG), a reactive α-oxoaldehyde, reacts with proteins to form irreversible advanced glycation end products (AGEs) following Maillard-like reaction. MG-induced AGE (MAGE) formation may be significant, particularly in diabetic condition with increased level of MG. Although myoglobin (Mb) is known to react with sugars to form AGEs, its interaction with MG is not known. Here we have studied interaction of Mb with MG. After in vitro reaction between Mb and MG at 25 °C for 7 days, the unchanged Mb and modified Mb (MG-Mb) were separated by ion exchange chromatography. Compared to Mb, MG-Mb exhibited higher electrophoretic mobility in native polyacrylamide gel electrophoresis, increased absorbance around 280 nm and more α-helical content, indicating structural changes of the modified protein. As shown by MALDI-mass spectrometry, MG converted Lys-16 and Lys-133 to carboxyethyllysine in MG-Mb. MAGE thus formed in MG-Mb may be associated with its enhanced mobility in native gel due to neutralization of positive charges and the observed structural changes in comparison with Mb.     

Identification of copper-zinc superoxide dismutase gene from enteroaggregative Escherichia coli.

We describe here the identification of sodC gene from enteroaggregative Escherichia coli (EAggEC). A 294 bp gene-specific fragment was amplified from the organism by DNA as well as RT-PCR using primers from bacterial sodC sequences. The metal co-factor present in the protein was confirmed by running samples in native gels and inhibiting with 2 mM potassium cyanide. However, the nonpathogenic E. coli possesses the gene but does not express it. Thus, the presence of copper-zinc superoxide dismutase encoded by sodC was demonstrated for the first time in EAggEC, which means it could be a novel candidate for a virulence marker.     

Solubilization, purification, and reconstitution of α2β1 isozyme of Na+/K+-ATPase from caveolae of pulmonary smooth muscle plasma membrane: comparative studies with DHPC, C12E8, and Triton X-100

We identified α₂, α₁, and β₁ isoforms of Na⁺/K⁺-ATPase in caveolae vesicles of bovine pulmonary smooth muscle plasma membrane. The biochemical and biophysical characteristics of the α₂β₁ isozyme of Na⁺/K⁺-ATPase from caveolae vesicles were studied during solubilization and purification using the detergents 1,2-heptanoyl-sn-phosphatidylcholine (DHPC), poly(oxy-ethylene)8-lauryl ether (C₁₂E₈), and Triton X-100, and reconstitution with the phospholipid dioleoyl-phosphatidylcholine (DOPC). DHPC was determined to be superior to C₁₂E₈, whereas C₁₂E₈ was better than Triton X-100 in the active enzyme yields and specific activity. Fluorescence studies with DHPC-purified α₂β₁ isozyme of Na⁺/K⁺-ATPase elicited higher E1Na?E2 K transition compared with that of the C₁₂E₈- and Triton X-100-purified enzyme. The rate of Na⁺ efflux in DHPC–DOPC-reconstituted isozyme was higher compared to the C₁₂E₈–DOPC- and Triton X100–DOPC-reconstituted enzyme. Circular dichroism analysis suggests that the DHPC-purified α₂β₁ isozyme of Na⁺/K⁺-ATPase possessed more organized secondary structure compared to the C₁₂E₈- and Triton X-100-purified isozyme.     

Effects of aspirin and paracetamol on ATPases of human fetal brain: an in vitro study

In vitro effects of aspirin and paracetamol at the doses 200, 400, 600, 800 nmole/mg protein on ATPases activity were studied in the cerebrum and cerebellum of human fetus covering the age range from 10 weeks to 32 weeks of gestation. Both aspirin and paracetamol inhibit Na+K+ ATPase and Mg2+ ATPase in a dose dependent manner. The inhibition of Na+K+ ATPase and Mg2+ ATPase activity which may affect the release and uptake of biogenic amines in CNS, hinders the maturation of human fetal brain.     

Role of phospholemman and the 70 kDa inhibitor protein in regulating Na/K ATPase activity in pulmonary artery smooth muscle cells under U46619 stimulation

Treatment of bovine pulmonary smooth muscle cells with U46619 inhibited the Na⁺/K⁺ ATPase activity in two parallel pathways: one of which is mediated via glutathionylation of the pump and the other by augmenting the inhibitory activity of the 70 kDa inhibitor protein of Na⁺/K⁺ ATPase. Although phospholemman deglutathionylates the pump leading to its activation, the inhibitor is responsible for irreversible inhibition of Na⁺/K⁺ ATPase in an isoform specific manner during treatment of the cells with U46619.     

Involvement of a serine esterase in oxidant-mediated activation of phospholipase A2 in pulmonary endothelium

Exposure of bovine pulmonary arterial endothelial cells to 1 mM H2O2 stimulated associated TAME-esterase and PLA2 activities. Pretreatment with the serine esterase inhibitors: PMSF (1 mM), DFP (1 mM), and alpha 1-PI (1 mg/ml) inhibited H2O2-induced stimulation of TAME-esterase and PLA2 activities. The TAME-esterase and PLA2 activities under H2O2 exposure were determined to be linearly correlated. Affinity labelling of the endothelial cell membrane with [3H]DFP demonstrated that the serine esterase resides in a protein having molecular weight of 29,000 daltons (29 kDa) which is similar to that of elastase. Treatment of the endothelial cell homogenate with trypsin (1 microgram/ml) also stimulated PLA2 activity.