Neutron scattering reveals the dynamic basis of protein adaptation to extreme temperature

To explore protein adaptation to extremely high temperatures, two parameters related to macromolecular dynamics, the mean square atomic fluctuation and structural resilience, expressed as a mean force constant, were measured by neutron scattering for hyperthermophilic malate dehydrogenase from Methanococcus jannaschii and a mesophilic homologue, lactate dehydrogenase from Oryctolagus cunniculus (rabbit) muscle. The root mean square fluctuations, defining flexibility, were found to be similar for both enzymes (1.5 A) at their optimal activity temperature. Resilience values, defining structural rigidity, are higher by an order of magnitude for the high temperature-adapted protein (0.15 Newtons/meter for O. cunniculus lactate dehydrogenase and 1.5 Newtons/meter for M. jannaschii malate dehydrogenase). Thermoadaptation appears to have been achieved by evolution through selection of appropriate structural rigidity in order to preserve specific protein structure while allowing the conformational flexibility required for activity.     

Bovine lactoferrin inhibits Influenza A virus induced programmed cell death in vitro

Influenza is one of the main plagues worldwide. The statistical likelihood of a new pandemic outbreak, together with the alarming emergence of influenza virus strains that are resistant to available antiviral medications, highlights the need for new antiviral drugs. Lactoferrin, a 80 kDa bi-globular iron-binding glycoprotein, is a pleiotropic factor with potent antimicrobial and immunomodulatory activities. Although the antiviral effect of lactoferrin is one of its major biological functions, the mechanism of action is still under debate. In this research, we have analyzed the effect of bovine lactoferrin (bLf) on Influenza A virus infection in vitro. Our results showed that (i) Influenza virus infected cells died as a result of apoptosis, (ii) bLf treatment inhibited programmed cell death by interfering with function of caspase 3, a major virus-induced apoptosis effector, and (iii) bLf efficiently blocked nuclear export of viral ribonucleoproteins so preventing viral assembly. These results provide further insights on the antiviral activity of bLf and suggest novel strategies for treatment of Influenza virus infection.     

Interplay of voltage and Ca-dependent inactivation of L-type Ca current

Inactivation of L-type Ca channels (LTCC) is regulated by both Ca and voltage-dependent processes (CDI and VDI). To differentiate VDI and CDI, several experimental and theoretical studies have considered the inactivation of Ba current through LTCC (I_Ba) as a measure of VDI. However, there is evidence that Ba can weakly mimic Ca, such that I_Ba inactivation is still a mixture of CDI and VDI. To avoid this complication, some have used the monovalent cation current through LTCC (I_NS), which can be measured when divalent cation concentrations are very low. Notably, I_NS inactivation rate does not depend on current amplitude, and hence may reflect purely VDI. However, based on analysis of existent and new data, and modeling, we find that I_NS can inactivate more rapidly and completely than I_Ba, especially at physiological temperature. Thus VDI that occurs during I_Ba (or I_Ca) must differ intrinsically from VDI during I_NS. To account for this, we have extended a previously published LTCC mathematical model of VDI and CDI into an excitation-contraction coupling model, and assessed whether and how experimental I_Ba inactivation results (traditionally used in VDI experiments and models) could be recapitulated by modifying CDI to account for Ba-dependent inactivation. Thus, the view of a slow and incomplete I_NS inactivation should be revised, and I_NS inactivation is a poor measure of VDI during I_Ca or I_Ba. This complicates VDI analysis experimentally, but raises intriguing new questions about how the molecular mechanisms of VDI differ for divalent and monovalent currents through LTCCs.     

A Systematic Review on the Development of Asthma and Allergic Diseases in Relation to International Immigration: The Leading Role of the Environment Confirmed

Background

The prevalence of asthma and allergic diseases is rising worldwide. Evidence on potential causal pathways of asthma and allergies is growing, but findings have been contradictory, particularly on the interplay between allergic diseases and understudied social determinants of health like migration status. This review aimed at providing evidence for the association between migration status and asthma and allergies, and to explore the mechanisms between migration status and the development of asthma and allergies.

Methods and Findings

Systematic review on asthma and allergies and immigration status in accordance with the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The pooled odds ratio (OR) of the prevalence of asthma in immigrants compared to the host population was 0.60 (95% CI 0.45–0.84), and the pooled OR for allergies was 1.01 (95% CI 0.62–1.69). The pooled OR for the prevalence of asthma in first generation versus second generation immigrants was 0.37 (95% CI 0.25–0.58). Comparisons between populations in their countries of origin and those that emigrated vary depending on their level of development; more developed countries show higher rates of asthma and allergies.

Conclusions

Our findings suggest a strong influence of the environment on the development of asthma and allergic diseases throughout the life course. The prevalence of asthma is generally higher in second generation than first generation immigrants. With length of residence in the host country the prevalence of asthma and allergic diseases increases steadily. These findings are consistent across study populations, host countries, and children as well as adults. Differences have been found to be significant when tested in a linear model, as well as when comparing between early and later age of migration, and between shorter and longer time of residence.     

Comparing the bioremoval of black crusts on colored artistic lithotypes of the Cathedral of Florence with chemical and laser treatment

The external walls of the Cathedral of Florence are made of green serpentine, red marlstone and Carrara white marble, and intensive air pollution attack has led to their weathering, which caused black crust formation. A study was performed to evaluate the most appropriate cleaning treatment for black crust removal, adopting chemical (ammonium carbonate poultice), laser (1064 nm, Nd:YAG laser), and microbial (poultice embedding sulfate-reducing bacteria) cleaning. The effects of the different procedures on the original surfaces were evaluated by scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and color measurements. One year later further color measurements were made. It was found that chemical cleaning led to non-homogeneous crust removal and that for the extremely powdery and incoherent red substratum the preferred treatment was laser cleaning. Overall, the most satisfactory treatment was the microbial cleaning process. It was the most controllable process and the most efficient for sulfate removal. Its main drawback appears to be the time needed to remove thick black crusts since numerous applications were necessary.     

Solution structure of Pisum sativum defensin 1 by high resolution NMR: plant defensins, identical backbone with different mechanisms of action.

Pisum sativum defensin 1 (Psd1) is a 46 amino acid residue plant defensin isolated from seeds of pea. The three-dimensional structure in solution of Psd1 was determined by two-dimensional NMR data recorded at 600 MHz. Experimental restraints were used for structure calculation using CNS and torsion-angle molecular dynamics. The 20 lowest energy structures were selected and further subjected to minimization, giving a root-mean-square deviation of 0.78(+/- 0.22) A in the backbone and 1.91(+/-0.60) A for over all atoms of the molecule. The protein has a globular fold with a triple-stranded antiparalell beta-sheet and an alpha-helix (from residue Asn17 to Leu27). Psd1 presents the so called "cysteine stabilized alpha/beta motif" and presents identical three-dimensional topology in the backbone with other defensins and neurotoxins. Comparison of the electrostatic surface potential among proteins with high three-dimensional (selected using the softwares TOP and DALI) topology gave insights into the mode of action of Psd1. The surface topologies between proteins that present antifungal activity or sodium channel inhibiting activity are different. On the other hand the surface topology presents several common features with potassium channel inhibitors, suggesting that Psd1 presents this activity. Other common features with potassium channel inhibitors were found including the presence of a lysine residue essential for inhibitory activity. The identity of Psd1 in primary sequence is not enough to infer a mechanism of action, in contrast with the strategy proposed here.     

Characterization of monomeric substates of ascorbate oxidase

Ascorbate oxidase (AAO) is a large, multidomain, dimeric protein whose folding/unfolding pathway is characterized by a complex, multistep process. Here we used fluorescence correlation spectroscopy to demonstrate the formation of partially folded monomers by pH-induced full dissociation into subunits. Hence, the structural features of monomeric AAO could be studied by fluorescence and CD spectroscopy. We found that the monomers keep their secondary structure, whereas subtle conformational changes in the tertiary structure become apparent. AAO dissociation has also been studied when unfolding the protein by high hydrostatic pressure at different pH values. A strong protein concentration dependence was observed at pH 8, whereas the enzyme was either monomeric or dimeric at pH 10 and 6, respectively. The calculated volume change associated with the unfolding of monomeric AAO, ΔV ～ -55 mL·mol(-1), is in the range observed for most proteins of the same size. These findings demonstrate that partially folded monomeric species might populate the energy landscape of AAO and that the overall AAO stability is crucially controlled by a few quaternary interactions at the subunits' interface.