Kinetics and computational studies of ligand migration in nitrophorin 7 and its Δ1–3 mutant

Nitrophorins (NPs) are nitric oxide (NO)-carrying heme proteins found in the saliva of the blood-sucking insect Rhodnius prolixus. Though NP7 exhibits a large sequence resemblance with other NPs, two major differential features are the ability to interact with negatively charged cell surfaces and the presence of a specific N-terminus composed of three extra residues (Leu1-Pro2-Gly3). The aim of this study is to examine the influence of the N-terminus on the ligand binding, and the topological features of inner cavities in closed and open states of NP7, which can be associated to the protein structure at low and high pH, respectively. Laser flash photolysis measurements of the CO rebinding kinetics to NP7 and its variant NP7(Δ1–3), which lacks the three extra residues at the N-terminus, exhibit a similar pattern and support the existence of a common kinetic mechanism for ligand migration and binding. This is supported by the existence of a common topology of inner cavities, which consists of two docking sites in the heme pocket and a secondary site at the back of the protein. The ligand exchange between these cavities is facilitated by an additional site, which can be transiently occupied by the ligand in NP7, although it is absent in NP4. These features provide a basis to explain the enhanced internal gas hosting capacity found experimentally in NP7 and the absence of ligand rebinding from secondary sites in NP4. The current data allow us to speculate that the processes of docking to cell surfaces and NO release may be interconnected in NP7, thereby efficiently releasing NO into a target cell. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.     

Summary of the 9th annual meeting of the italian society for virology

The 9th annual meeting of the Italian Society for Virology (SIV) comprised seven plenary sessions focused on: General virology and viral genetics; Virus–Host interaction and pathogenesis; Viral oncology; Emerging viruses and zoonotic, foodborne, and environmental pathways of transmission; Viral immunology and vaccines; Medical virology and antiviral therapy; Viral biotechnologies and gene therapy. Moreover, four hot topics were discussed in special lectures: the Pioneer in human virology lecture regarding the control of viral epidemics with particular emphasis on the human immunodeficiency virus (HIV), the Pioneer in plant virology lecture focused on cell responses to plant virus infection, a Keynote lecture on the epidemiology and genetic diversity of Crimea–Congo Hemorrhagic Fever virus, and the G.B. Rossi lecture on the molecular basis and clinical implications of human cytomegalovirus tropism for endothelial/epithelial cells. The meeting had an attendance of about 160 virologists. A summary of the plenary lectures and oral selected presentations is reported. J. Cell. Physiol. 226: 285–287, 2010. © 2010 Wiley‐Liss, Inc.     

Hazara virus and Crimean-Congo Hemorrhagic Fever Virus show a different pattern of entry in fully-polarized Caco-2 cell line

Crimean-Congo Hemorrhagic Fever Virus (CCHFV) and Hazara virus (HAZV) belong to the same viral serotype and family. HAZV has lately been used as a model system and surrogate to CCHFV. However, virus-host cell interaction and level of pathogenicity for these viruses are not well investigated nor compared. In this study, we compared HAZV and CCHFV infection of human polarized epithelial cells to shed light on similarities and differences in virus-host cell interaction between these two viruses. We investigated the pattern of infection of CCHFV and HAZV in fully polarized human cells, the Caco-2 cell line. Polarization of Caco-2 cells lead to difference in expression level and pattern of proteins between the apical and the basolateral membranes. We found that CCHFV virus, in contrast to HAZV, is more likely infecting polarized cells basolaterally. In addition, we found that cytokines/pro-inflammatory factors or other viral factors secreted from CCHFV infected moDC cells enhance the entry of CCHFV contrary to HAZV. We have shown that CCHFV and HAZV early in infection use different strategies for entry. The data presented in this study also highlight the important role of cytokines in CCHFV-host cell interaction.     

Role of Brazilian zoos in ex situ bird conservation: from 1981 to 2005

Zoos may play an important role in conservation when they maintain and breed large numbers of animals that are threatened with extinction. Bird conservation is in a privileged situation owing to the extensive biological information available about this class. Annual inventories produced by the "Sociedade de Zoológicos do Brasil" in the years 1981, 1990, 2000, and 2005 were analyzed. Variables, such as the number of zoos per geographic region; number of birds held; number of bird species in each IUCN threat category; number of exotic and native bird species; number of potentially breeding bird species; number of bird species in each order; and number of threatened bird species breeding, were analyzed. Brazilian zoos kept more than 350 bird species. The number of bird species and specimens held by the Brazilian Zoos increased from 1981 to 2000, but decreased in 2005. The same pattern was observed for the number of species in each IUCN threat category. Results showed that the potential of the Brazilian zoos in bird conservation needs to be enhanced because they maintain threatened species but do not implement systematic genetic, reproductive, or behavioral management protocols for most species.     

The Deoxynucleoside Triphosphate Triphosphohydrolase Activity of SAMHD1 Protein Contributes to the Mitochondrial DNA Depletion Associated with Genetic Deficiency of Deoxyguanosine Kinase

The dNTP triphosphohydrolase SAMHD1 is a nuclear antiviral host restriction factor limiting HIV-1 infection in macrophages and a major regulator of dNTP concentrations in human cells. In normal human fibroblasts its expression increases during quiescence, contributing to the small dNTP pool sizes of these cells. Down-regulation of SAMHD1 by siRNA expands all four dNTP pools, with dGTP undergoing the largest relative increase. The deoxyguanosine released by SAMHD1 from dGTP can be phosphorylated inside mitochondria by deoxyguanosine kinase (dGK) or degraded in the cytosol by purine nucleoside phosphorylase. Genetic mutations of dGK cause mitochondrial (mt) DNA depletion in noncycling cells and hepato-cerebral mtDNA depletion syndrome in humans. We studied if SAMHD1 and dGK interact in the regulation of the dGTP pool during quiescence employing dGK-mutated skin fibroblasts derived from three unrelated patients. In the presence of SAMHD1 quiescent mutant fibroblasts manifested mt dNTP pool imbalance and mtDNA depletion. When SAMHD1 was silenced by siRNA transfection the composition of the mt dNTP pool approached that of the controls, and mtDNA copy number increased, compensating the depletion to various degrees in the different mutant fibroblasts. Chemical inhibition of purine nucleoside phosphorylase did not improve deoxyguanosine recycling by dGK in WT cells. We conclude that the activity of SAMHD1 contributes to the pathological phenotype of dGK deficiency. Our results prove the importance of SAMHD1 in the regulation of all dNTP pools and suggest that dGK inside mitochondria has the function of recycling the deoxyguanosine derived from endogenous dGTP degraded by SAMHD1 in the nucleus.     

Development of a new method for simultaneous extraction of chlorophylls and carotenoids from microalgal biomass

Journal of Applied Phycology - There are still limitations in the pigment extraction methods used in microalgae biomass, especially for laboratory scale. This work aimed to develop a simple method...     

Inferred kinship patterns reveal low levels of extra-pair paternity in the endangered Neotropical Jabiru Stork (Jabiru mycteria, Aves: Ciconiiformes)

The present study inferred the genetic mating system in a natural breeding population of the Jabiru Stork (Jabiru mycteria), a Neotropical wading bird considered endangered in part of its distribution range. Based on data from eight microsatellite loci, maximum-likelihood kinship reconstruction techniques, parentage assignment analyses and effective population size (Ne) estimates were applied to samples collected in the Brazilian Pantanal wetland (N = 45 nestlings from 20 nests; N = 17 shed adult feathers from 11 nests). The relationship diagnosis was determined for most of the complete clutches (86.66 %): 92.31 % were full siblings and 7.69 % were half siblings. Shed feathers collected from the nests matched the genetic parents of the offspring in 80 % of cases. Feathers collected from the ground below the nests were compatible with the putative parents in 41.67 % of cases. A mean Ne of 35 reproductive individuals was inferred, corresponding to an Ne/Nc ratio of 0.09, which is similar to the ratio found in populations of a number of different wild animals. The higher proportion of full siblings identified in the broods suggests that genetic monogamy is the prevalent mating system in the Jabiru Stork, while the detection of half siblings suggests some degree of extra-pair paternity. The present findings are in agreement with previous ecological observations of social monogamy in this species, despite the isolated evidence of extra-pair copulation events. This study also demonstrates the usefulness of a noninvasive approach to sampling adults and performing parentage and relatedness analyses in an elusive, threatened species.