UVB-dependent generation of reactive oxygen species by catalase and IgG under UVB light: Inhibition by antioxidants and anti-inflammatory drugs

Catalase, which can decompose H2O2, has recently been found to generate unspecified reactive oxygen species (ROS) as a result of ultraviolet B (UVB) irradiation. Many proteins, hemes, and iron compounds were first tested to determine that this ROS generation was unique to catalase and immunoglobulin G (IgG). An increase in absorbance at 502 nm due to 2',7'-dichlorofluorescein, the oxidized product of 2',7'-dichlorodihydrofluorecein diacetate as a result of UVB (310 nm) irradiation, was measured in order to estimate this ROS generation. Catalase and IgG generated a pronounced amount of ROS when irradiated with UVB. Another heme protein, cytochrome c, and heat-inactivated catalase had no such effect. ROS generation by catalase was at least 5 times more potent than that reported for IgG with UVB and without antigens. This catalasemediated ROS generation was largely temperaturedependent in the range of 25 to 42°C. As IgG is considered an evolutionally important bactericidal component, the same was considered true for this enzyme. Next, inhibitory effects of various drugs, including antioxidants and anti-inflammatory drugs, on catalase-mediated and UVB-induced ROS generation were examined. Many of the drugs, including catalase inhibitors, had inhibitory effects with different potencies. Melanin was found to be the most effective inhibitor of this ROS generation (IC(30), 0.2 μg/mL), followed by Indigo Carmine and rutin. Also inhibiting this ROS generation were ascorbic acid, α-tocopherol, indomethacin, coenzyme Q10, β-carotene, uric acid, piroxicam, diclofenac, and glutathione, in that order of potency. Various ROS were apparently generated by catalase under UVB, creating a cycle or chain which was thought due to the biphasic effects of some drugs such as 3-aminotriazole or sodium azide. Excess ROS generation induces inflammation. Catalase might serve dual roles, removing H2O2 and generating various ROS depending on the H2O2 concentration and other factors.

Vascular endothelial growth factor expression in rat skin incision wound

Vascular endothelial growth factor (VEGF) is a glycoprotein that enhances vascular permeability, induces chemotaxis and activation of monocytes/macrophages, and promotes growth of vascular endothelial cells. We report that infiltrating polymorphonuclear leukocytes in an incision wound in rat skin express VEGF from 1 day after the injury, as shown by immunohistochemistry. VEGF is also present in macrophages, fibroblast-like cells, and endothelial cells 3 and 7 days after the injury. mRNA for VEGF is statistically significantly increased in the wound area in the tissue 1 day after the skin incision compared with 3 and 7 days after the incision. The VEGF protein content in the wound tissue is statistically significantly higher in the wound than in control skin at 1 and 3 days after skin incision. Our results indicate that VEGF is produced by inflammatory cells to induce vascularization in the early stage of the wound healing process.

Three isoforms of cyclophilin A associated with human immunodeficiency virus type 1 were found by proteomics by using two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization-time of flight mass spectrometry

Human immunodeficiency virus type 1 (HIV-1) strain LAV-1 (HIV-1(LAV-1)) particles were collected by ultracentrifugation, treated with subtilisin, and then purified by Sepharose CL-4B column chromatography to remove microvesicles. The lysate of the purified HIV-1(LAV-1) particles was subjected to two-dimensional (2D) gel electrophoresis and stained. The 2D gel electrophoresis image suggested that 24 proteins can be identified inside the virion. Furthermore, the stained protein spots were excised and digested with trypsin. The resulting peptide fragments were characterized by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Peptide mass fingerprinting data suggested that two isoforms of cyclophilin A (CyPA), one with an isoelectric point (pI) of 6.40 and one with a pI of 6.53, are inside the viral membrane; that another isoform, with a pI of 6.88, is outside the viral membrane; and that the CyPA isoform with a pI of 6.53 is N acetylated. The mechanisms that permit the redistribution of CyPA on the viral surface have not yet been clarified, but it is surmised that the CyPA isoform with a pI of 6.88 may play a critical role in the attachment of virions to the surface of target cells and that both CyPA isoforms with pIs of 6.40 and 6.53 may regulate the conformation of the HIV-1 capsid protein.

Acid-labile formylation of amino terminal proline of human immunodeficiency virus type 1 p24(gag) was found by proteomics using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry

HIV-1(LAV-1) particles were collected by ultracentrifugation, treated with subtilisin, and then purified by Sepharose CL-4B column chromatography to remove microvesicles. The lysate of the purified human immunodeficiency virus type 1 (HIV-1) particles was subjected to two-dimensional (2D) gel electrophoresis and stained, and the stained spots were excised and digested with trypsin. The resulting peptide fragments were characterized by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-five proteins were identified as the proteins inside the virion and the acid-labile formyl group of an amino terminal proline residue of HIV-1(LAV-1) p24(gag) was determined by MALDI-TOF MS before and after weak-acid treatments (0.6 N hydrochloric acid) and confirmed by post-source decay (PSD) of the N-formylated N-terminal tryptic peptide (N-formylated Pro(1)-Arg(18)). The role of formylation has been unclear so far, but it is surmised that the acid-labile formylation of HIV-1(LAV-1) p24(gag) may play a critical role in the formation of the HIV-1 core for conferring HIV-1 infectivity.

Myristoylation of human immunodeficiency virus type 1 gag protein is required for efficient env protein transportation to the surface of cells

Highly conserved amino acids in the N-terminal region of the human immunodeficiency virus type 1 (HIV-1) Pr55(gag) are recognized to be critical for the attachment of myristic acid. We previously reported that the env protein was not detected on the cell surface by blocking of N-myristoylation of Pr55(gag) with N-myristoyl glycinal diethylacetal. Here, we constructed a mutant by substituting the N-terminal glycine of Pr55(gag) with alanine to demonstrate that N-myristoylation of Pr55(gag) is required for efficient env protein transportation to the cell surface. The expression level of the env protein on the surface of Jurkat cells transfected with the myristoylation-defective phenotype was observed to be significantly reduced by electron microscopic analyses with a gold-labeled monoclonal antibody against the env protein. In addition, Jurkat cells transfected with the myristoylation-defective phenotype lost the ability of envelope-mediated cell-to-cell fusion. The results suggest that N-myristoylation of the HIV-1 gag protein is necessary for efficient env protein transportation to the cell surface.

Blockage of N-myristoylation of HIV-1 gag induces the production of impotent progeny virus

The role of the N-myristoylation of the human immunodeficiency virus type 1 (HIV-1) gag protein in ACH-2 cells was studied. The infectivity of HIV-1 from the cells stimulated with phorbol 12-myristate 13-acetate (PMA) was suppressed by pretreatment with N-myristoyl glycinal diethylacetal (N-Myr-GOA), a potent N-myristoylation inhibitor, and the blockage of myristoylation resulted in accumulation of immature gag precursors. The viral particles which budded from the non-N-Myr-GOA-treated ACH-2 cells stimulated with PMA exhibited a typical viral phenotype, whereas those which budded from the N-Myr-GOA-treated ACH-2 cells stimulated with PMA were twisted, as observed electron microscopically. In electron microscopic analyses with gold-labeled monoclonal antibodies to gag and env, gag and env were detected adjacent to each other in the PMA-stimulated ACH-2, but no env was detected in the cells treated with N-Myr-GOA. Taken together, the results suggest that the myristoylation of HIV-1 gag seems to be responsible for both maturation of gag and acquisition of HIV-1 infectivity.

Histochemical localization of copper in the intestine and kidney of macular mice: light and electron microscopic study

Menkes' disease is an X-linked recessive disorder characterized by accumulation of copper in various organs and cells, such as the intestine, kidney, and cultured fibroblasts. Light and electron microscopic localization of Cu was investigated in the intestine and kidney of macular mice, an animal model of Menkes' disease, by a modified sulfide-silver method. Cu was accumulated in the cytoplasm of the absorptive epithelial cells, the vascular endothelium, and secretory granules of the Paneth cells. In kidney the distal tubule cells and glomeruli of both macular and control mice stained faintly, whereas the organelle-free cytoplasm in the proximal tubule cells of macular mice stained more intensely than those of controls. The nuclei, mitochondria, and lysosomes of the cells of macular mice hardly stained at all. These findings indicate that Cu is concentrated in the organelle-free cytoplasm of the affected cells of macular mice. This suggests that the Menkes' mutation affects Cu transport from the cytosol to the organelles in the cell.

1H NMR studies on the catalytic subunit of aspartate transcarbamoylase

The 1H NMR spectrum of the catalytic subunit of Escherichia coli aspartate transcarbamoylase (EC 2.1.3.2) was simplified by using strains auxotrophic for the aromatic amino acids and a growth medium containing fully deuterated Trp, Phe, and His and partially deuterated Tyr. 1H resonances for Tyr in the catalytic trimer (M(r) = 10(5)) were partially resolved into five peaks at 27 degrees C, which above 50 degrees C were further resolved to give a distinct resonance for each of the eight Tyr residues in the polypeptide chain. Experiments on chemically modified catalytic subunits and on a mutant form in which Tyr-165 was converted to Ser-165 led to the assignment of resonances for Tyr-165, Tyr-240, and Tyr-185. Binding of the substrate, carbamoyl phosphate, caused shifts of two of the unassigned resonances, and the subsequent binding of the aspartate analog succinate perturbed the resonances corresponding to Tyr-165 and Tyr-240. The bisubstrate analog N-(phosphonacetyl)-L-aspartate produced a spectrum differing considerably from that caused by the combination of carbamoyl phosphate and succinate. The NMR spectrum for the Tyr-165-->Ser mutant trimer showed clearly that the single amino acid substitution caused conformational changes affecting the environment of residues remote from the position of the replacement. In contrast, the inactive mutant subunit in which Gly-128 was replaced by Asp exhibited a spectrum virtually identical to that of the wild-type protein. However, addition of the substrate carbamoyl phosphate caused a marked change in the spectrum of the mutant enzyme, whereas that of the wild-type trimer was altered only slightly, showing that the effect of the amino acid substitution was manifested in the NMR spectrum only with the liganded enzyme.

Effect of ATP on glucose-6-phosphate isomerase from Bacillus caldotenax

Glucose-6-phosphate isomerase (D-glucose-6-phosphate ketol-isomerase, EC 5.3.1.9) from Bacillus caldotenax exhibits negative cooperativity in enzyme activity. Fructose 1-phosphate, fructose, 1,6-bisphosphate, phosphoenolpyruvate, 6-phosphogluconate, 3-phosphoglycerate, ATP and Pi competitively inhibit the enzyme and abolish negative cooperativity in enzyme activity, while glucose 1-phosphate, dihydroxyacetone phosphate, glyceraldehyde 3-phosphate, ADP and AMP do not inhibit the enzyme. Among the inhibitors of which intracellular concentrations can be measured, only ATP inhibits the enzyme and abolishes negative cooperativity in enzyme activity at intracellular concentration. Such ATP inhibition is observed at 65 degrees C, but not at 30 degrees C, and the inhibition becomes less effective as the temperature decreases.

Purification and some properties of 6-phosphoglucose isomerase from Bacillus caldotenax

6-Phosphoglucose isomerase [EC 5.3.1.9] was purified from Bacillus caldotenax. The isomerase shared many common properties with the isomerase from B. stearothermophilus, i.e, pH and temperature optima, thermostability, competitive inhibition by 6-phosphogluconate and Pi, and amino acid composition. The enzyme activity of the former, however, was lower than that of the latter. The molecular weight of the B. caldotenax isomerase was estimated to be 202,000-204,000 by gel filtration and electrophoresis of the enzyme cross-linked with dimethyl adipimidate (DMA). The enzyme was shown to consist of four subunits of equal molecular weight (50,600), and the four subunits were concluded to be identical based on the results of dansylation and cyanogen bromide cleavage of the enzyme. The interaction between the subunits were shown to be isologous by cross-linking with DMA.

Acidostability of speroplasts prepared from Thiobacillus thiooxidans

Thiobacillus thiooxidans was acidostable even in the absence of its respiratory substrate, elementary sulfur. This suggests that the acidostability of the bacterium was enery-independent. The organism was subjected to osmotic shock with 0.75 M sucrose at 0 degrees C and then treated with snail intestinal juice in the presence of 0.3 M sucrose. The decrease in the optical density of the sample thus prepared on dilution with deionized water and electron microscopic observation of the sample showed that spheroplasts were formed from the bacterium by this procedure. Spheroplasts were able to respire sulfur and their respiratory activity was acidostable. Spheroplasts, when treated with Nagase, proteolytic enzyme, lost their acidostability, and some protein components disappeared from the membrane fraction. This suggests that the acidostability of the bacterium may be related to protein conponents of the membrane.