Crystal structures of the NO- and CO-bound heme oxygenase from Neisseriae meningitidis. Implications for O2 activation

Heme oxygenases catalyze the oxidation of heme to biliverdin, carbon monoxide, and free iron while playing a critical role in mammalian heme homeostasis. Pathogenic bacteria such as Neisseriae meningitidis also produce heme oxygenase as part of a mechanism to mine host iron. The key step in heme oxidation is the regioselective oxidation of the heme alpha-meso-carbon by an activated Fe(III)-OOH complex. The structures of various diatomic ligands bound to the heme iron can mimic the dioxygen complex and provide important insights on the mechanism of O2 activation. Here we report the crystal structures of N. meningitidis heme oxygenase (nm-HO) in the Fe(II), Fe(II)-CO, and Fe(II)-NO states and compare these to the NO complex of human heme oxygenase-1 (Lad, L., Wang, J., Li, H., Friedman, J., Bhaskar, B., Ortiz de Montellano, P. R., and Poulos, T. L. (2003) J. Mol. Biol. 330, 527-538). Coordination of NO or CO results in a reorientation of Arg-77 that enables Arg-77 to participate in an active site H-bonded network involving a series of water molecules. One of these water molecules directly H-bonds to the Fe(II)-linked ligand and very likely serves as the proton source required for oxygen activation. Although the active site residues differ between nm-HO and human HO-1, the close similarity in the H-bonded water network suggests a common mechanism shared by all heme oxygenases.     

Decreased formation of inositol trisphosphate in Madin-Darby canine kidney cells under conditions of beta-glucosidase inhibition.

Recent work has demonstrated the enhancement of hormone-stimulated inositol trisphosphate formation in renal epithelial cells under conditions of glucosylceramide depletion. The role of glucosylceramide metabolism was explored further by exposing Madin-Darby canine kidney (MDCK) cells to the beta-glucosidase inhibitor conduritol B epoxide, which produced time-dependent and concentration-dependent increases in glucosylceramide levels and decreased bradykinin-stimulated inositol trisphosphate formation from isolated MDCK cell membranes. These data provide further support for an association between glucosylceramide levels and hormone-stimulated inositol trisphosphate formation.     

Effect of fatty acids on cellulase production by Penicillium funiculosum and its mutants

Summary Penicillium funiculosum and its mutants namely BU-36 and N-4 responded differently to the addition of fatty acids. Addition of 0.1% oleic, linoleic, and linolenic acids resulted in significant increase in extracellular exo-glucanase and -glucosidase in wild and N-4 strains, whereas no appreciable increase was noticed in BU-36. However, BU-36 showed positive response with 0.1% palmitic and stearic acids. In all the strains, the addition of different fatty acids did not have any effect on endoglucanase activity. Our results indicate that fatty acids do have a role in the release of the cell-bound cellulolytic enzymes.NCL Communication No. : 4113     

Bacterial Diversity of Lonar Soda Lake of India

Total seventy four bacteria were isolated from Lonar soda lake of Maharashtra state, India. Eleven isolates were identified using morphological, biochemical and molecular analysis. The bacteria isolated belonged to phylum firmicutes and proteobacteria. Majorities (eight) were firmicutes and three were proteobacteria. For the first time we are reporting Alcanivorax spp. which is a genus well known for its oil degradation capacity, indicate the probable existence of oil reservoir in vicinity of Lonar lake. In addition all the eleven bacteria are potential producers of industrially important enzymes, pigments, antibiotics as well.     

Increases in coronary vein CO2 during cardiac resuscitation

We investigated the aortic, mixed venous, and great cardiac vein acid-base changes in eight domestic pigs during cardiac arrest produced by ventricular fibrillation and during cardiopulmonary resuscitation (CPR). The great cardiac vein PCO2 increased from a control value of 52 +/- 2 to 132 +/- 28 (SD) Torr during CPR, whereas the arterial PCO2 was unchanged (39 +/- 4 vs. 38 +/- 4). The coronary venoarterial PCO2 gradient, therefore, increased remarkably from 13 +/- 2 to 94 +/- 29 Torr. The simultaneously measured great cardiac vein lactate concentrations increased from 0.24 +/- 0.06 to 7.3 +/- 2.34 mmol/l. Much more moderate increases in the lactate content of aortic blood from 0.64 +/- 0.25 to 2.56 +/- 0.27 mmol/l were observed. Increases in great cardiac vein PCO2 and lactate were highly correlated during CPR (r = 0.91). After successful CPR, the coronary venoarterial PCO2 gradient returned to normal levels within 2 min after restoration of spontaneous circulation. Lactate content was rapidly reduced and lactate extraction was reestablished within 30 min after CPR. These studies demonstrate marked but reversible acidosis predominantly as the result of myocardial CO2 production during CPR.     

Impact of forest plantation on methane emissions from tropical peatland

Tropical peatlands are a known source of methane (CH₄) to the atmosphere, but their contribution to atmospheric CH₄ is poorly constrained. Since the 1980s, extensive areas of the peatlands in Southeast Asia have experienced land‐cover change to smallholder agriculture and forest plantations. This land‐cover change generally involves lowering of groundwater level (GWL), as well as modification of vegetation type, both of which potentially influence CH₄ emissions. We measured CH₄ exchanges at the landscape scale using eddy covariance towers over two land‐cover types in tropical peatland in Sumatra, Indonesia: (a) a natural forest and (b) an Acacia crassicarpa plantation. Annual CH₄ exchanges over the natural forest (9.1 ± 0.9 g CH₄ m^?2 year^?1) were around twice as high as those of the Acacia plantation (4.7 ± 1.5 g CH₄ m^?2 year^?1). Results highlight that tropical peatlands are significant CH₄ sources, and probably have a greater impact on global atmospheric CH₄ concentrations than previously thought. Observations showed a clear diurnal variation in CH₄ exchange over the natural forest where the GWL was higher than 40 cm below the ground surface. The diurnal variation in CH₄ exchanges was strongly correlated with associated changes in the canopy conductance to water vapor, photosynthetic photon flux density, vapor pressure deficit, and air temperature. The absence of a comparable diurnal pattern in CH₄ exchange over the Acacia plantation may be the result of the GWL being consistently below the root zone. Our results, which are among the first eddy covariance CH₄ exchange data reported for any tropical peatland, should help to reduce the uncertainty in the estimation of CH₄ emissions from a globally important ecosystem, provide a more complete estimate of the impact of land‐cover change on tropical peat, and develop science‐based peatland management practices that help to minimize greenhouse gas emissions.     

Genetic mapping refines DFNB3 to 17p11.2, suggests multiple alleles of DFNB3, and supports homology to the mouse model shaker-2.

The nonsyndromic congenital recessive deafness gene, DFNB3, first identified in Bengkala, Bali, was mapped to a approximately 12-cM interval on chromosome 17. New short tandem repeats (STRs) and additional DNA samples were used to identify recombinants that constrain the DFNB3 interval to less, similar6 cM on 17p11.2. Affected individuals from Bengkala and affected members of a family with hereditary deafness who were from Bila, a village neighboring Bengkala, were homozygous for the same alleles for six adjacent STRs in the DFNB3 region and were heterozygous for other distal markers, thus limiting DFNB3 to an approximately 3-cM interval. Nonsyndromic deafness segregating in two unrelated consanguineous Indian families, M21 and I-1924, were also linked to the DFNB3 region. Haplotype analysis indicates that the DFNB3 mutations in the three pedigrees most likely arose independently and suggests that DFNB3 makes a significant contribution to hereditary deafness worldwide. On the basis of conserved synteny, mouse deafness mutations shaker-2 (sh2) and sh2J are proposed as models of DFNB3. Genetic mapping has refined sh2 to a 0.6-cM interval of chromosome 11. Three homologous genes map within the sh2 and DFNB3 intervals, suggesting that sh2 is the homologue of DFNB3.     

Tumor Necrosis Factor-α Sensitizes Breast Cancer Cells to Natural Products with Proteasome-Inhibitory Activity Leading to Apoptosis

The inflammatory microenvironment plays an important role in the process of tumor development. Tumor necrosis factor-α (TNF-α), a key pro-inflammatory cytokine, has a significant role in this process. Natural medicinal products such as Withaferin A (WA) and Celastrol (Cel) have shown anti-cancer and anti-inflammatory properties that can be attributed to multiple mechanisms including, but not limited to, apoptosis induction due to the inhibition of proteasomal activities. This study aimed to investigate the effects of TNF-α in combination with WA or Cel in vitro in MDA-MB-231 breast cancer cells. TNF-α, when combined with WA or Cel, activated caspase-3 and -9 and downregulated XIAP in a dose-dependent manner, leading to induction of apoptosis in MDA-MB-231 breast cancer cells. The combination also caused accumulation of the proteasomal target protein IκBα, resulting in inhibition of the nuclear translocation of nuclear factor-κB (NF-κB). Taken together, these results suggest that TNF-α could sensitize breast cancer cells MDA-MB-231 to WA and Cel, at least in part, through inhibiting the activation of NF-κB signaling, leading to XIAP inhibition with subsequent upregulation of caspase-3 and -9 activities. Thus, the anti-cancer activities of TNF-α are enhanced when combined with the natural proteasome inhibitors, WA or Cel.     

Incidence of Keratinophilic Fungi from the Selected Soils of Kaziranga National Park,Assam (India)

Seventy-eight soil samples were collected from the various locations in the vicinity of Kaziranga National Park (Assam), India, during April to October 2009 and screened for the presence of keratinophilic fungi using the hair baiting techniques for isolation. Thirty-nine isolates were recovered and identified by recognition of their macro- and micromorphological features. Their identification was also confirmed by the BLAST search of sequences of the ITS1-5.8S-ITS2 rDNA region against the NCBI/GenBank data and compared with deposited sequences for identification purpose. Eleven species related to seven genera were recorded viz. Aphanoascus durus (1.28%), Arthroderma tuberculatum (3.84%), Arthroderma corniculatum (1.28%), Chrysosporium indicum (16.66%), C. tropicum (3.84%), Ctenomyces serratus (5.12%), Keratinophyton punsolae (1.28%), Microsporum appendiculatum (1.28%), Microsporum gypseum complex (11.53%), Trichophyton mentagrophytes (11.28%) and T. terrestre (2.56%).