W-F substitutions in apomyoglobin increase the local flexibility of the N-terminal region causing amyloid aggregation: A H/D exchange study.

Myoglobin is an α-helical globular protein containing two highly conserved tryptophanyl residues at positions 7 and 14 in the N-terminal region. The simultaneous substitution of the two residues impairs the productive folding of the protein making the polypeptide chain highly prone to aggregate forming amyloid fibrils at physiological pH and room temperature. The role played by tryptophanyl residues in driving the productive folding process was investigated by providing structural details at low resolution of compact intermediate of three mutated apomyoglobins, i.e., W7F, W14F and the amyloid forming mutant W7FW14F. In particular, we followed the hydrogen/deuterium exchange rate of protein segments using proteolysis with pepsin followed by mass spectrometry analysis. The results revealed significant differences in the N-terminal region, consisting in an alteration of the physico-chemical properties of the 7-11 segment for W7F and in an increase of local flexibility of the 12-29 segment for W14F. In the double trypthophanyl substituted mutant, these effects are additive and impair the formation of native-like contacts and favour inter-chain interactions leading to protein aggregation and amyloid formation at physiological pH

Suppressor of cytokine signaling (SOCS)5 ameliorates influenza infection via inhibition of EGFR signaling

© Kedzierski et al. Influenza virus infections have a significant impact on global human health. Individuals with suppressed immunity, or suffering from chronic inflammatory conditions such as COPD, are particularly susceptible to influenza. Here we show that suppressor of cytokine signaling (SOCS) five has a pivotal role in restricting influenza A virus in the airway epithelium, through the regulation of epidermal growth factor receptor (EGFR). Socs5-deficient mice exhibit heightened disease severity, with increased viral titres and weight loss. Socs5 levels were differentially regulated in response to distinct influenza viruses (H1N1, H3N2, H5N1 and H11N9) and were reduced in primary epithelial cells from COPD patients, again correlating with increased susceptibility to influenza. Importantly, restoration of SOCS5 levels restricted influenza virus infection, suggesting that manipulating SOCS5 expression and/or SOCS5 targets might be a novel therapeutic approach to influenza

Domain organization of phytochelatin synthase: functional properties of truncated enzyme species identified by limited proteolysis

Phytochelatin synthase (PCS) is a major determinant of heavy metal tolerance in plants and other organisms. No structural information on this enzyme is as yet available. It is generally believed, however, that the active site region is located in the more conserved N-terminal portion of PCS, whereas various, as yet unidentified (but supposedly less critical) roles have been proposed for the C-terminal region. To gain insight into the structural/functional organization of PCS, we have conducted a limited proteolysis analysis of the enzyme from Arabidopsis (AtPCS1), followed by functional characterization of the resulting polypeptide fragments. Two N-terminal fragments ending at positions 372 (PCS_Nt1) and 283 (PCS_Nt2) were produced sequentially upon V8 protease digestion, without any detectable accumulation of the corresponding C-terminal fragments. As revealed by the results of in vivo and in vitro functional assays, the core PCS_Nt2 fragment is biosynthetically active in the presence of cadmium ions and supports phytochelatin formation at a rate that is only approximately 5-fold lower than that of full-length AtPCS1. The loss of the C-terminal region, however, substantially decreases the thermal stability of the enzyme and impairs phytochelatin formation in the presence of certain heavy metals (e.g. mercury and zinc, but not cadmium or copper). The latter phenotype was shared by PCS_Nt2 and by its precursor fragment PCS_Nt1, which, on the other hand, was almost as stable and biosynthetically active (in the presence of cadmium) as the full-length enzyme. AtPCS1 thus appears to be composed of a protease-resistant (and hence presumably highly structured) N-terminal domain, flanked by an intrinsically unstable C-terminal region. The most upstream part of such a region (positions 284-372) is important for enzyme stabilization, whereas its most terminal part (positions 373-485) appears to be required to determine enzyme responsiveness to a broader range of heavy metals

Resolution of the effects induced by W → F substitutions on the conformation and dynamics of the amyloid-forming apomyoglobin mutant W7FW14F.

Myoglobin is an alpha-helical globular protein containing two highly conserved tryptophanyl residues at positions 7 and 14 in the N-terminal region. The simultaneous substitution of the two residues increases the susceptibility of the polypeptide chain to misfold, causing amyloid aggregation under physiological condition, i.e., neutral pH and room temperature. The role played by tryptophanyl residues in driving the folding process has been investigated by examining three mutated apomyoglobins, i.e., W7F, W14F, and the amyloid-forming mutant W7FW14F, by an integrated approach based on far-ultraviolet (UV) circular dichroism (CD) analysis, fluorescence spectroscopy, and complementary proteolysis. Particular attention has been devoted to examine the conformational and dynamic properties of the equilibrium intermediate formed at pH 4.0, since it represents the early organized structure from which the native fold originates. The results show that the W → F substitutions at position 7 and 14 differently affect the structural organization of the AGH subdomain of apomyoglobin. The combined effect of the two substitutions in the double mutant impairs the formation of native-like contacts and favors interchain interactions, leading to protein aggregation and amyloid formation

Resolution of the effects induced by W → F substitutions on the conformation and dynamics of the amyloid-forming apomyoglobin mutant W7FW14F.

""Myoglobin is an alpha-helical globular protein containing two highly conserved tryptophanyl residues at positions 7 and 14 in the N-terminal region. The simultaneous substitution of the two residues increases the susceptibility of the polypeptide chain to misfold, causing amyloid aggregation under physiological condition, i.e., neutral pH and room temperature. The role played by tryptophanyl residues in driving the folding process has been investigated by examining three mutated apomyoglobins, i.e., W7F, W14F, and the amyloid-forming mutant W7FW14F, by an integrated approach based on far-ultraviolet (UV) circular dichroism (CD) analysis, fluorescence spectroscopy, and complementary proteolysis. Particular attention has been devoted to examine the conformational and dynamic properties of the equilibrium intermediate formed at pH 4.0, since it represents the early organized structure from which the native fold originates. The results show that the W -> F substitutions at position 7 and 14 differently affect the structural organization of the AGH subdomain of apomyoglobin. The combined effect of the two substitutions in the double mutant impairs the formation of native-like contacts and favors interchain interactions, leading to protein aggregation and amyloid formation."

The co-chaperone BAG3 interacts with the cytosolic chaperonin CCT: new hints for actin folding

It has been recently hypothesized that BAG3 protein, a co-chaperone of Hsp70/Hsc70, is involved in the regulation of several cell processes, such as apoptosis, autophagy and cell motility. Following the identification of Hsc70/Hsp70, further BAG3 molecular partners such as PLC- and HspB8 were likewise identified, thus contributing to the characterization of the mechanisms and the biological roles carried out by this versatile protein. By using a His-tagged BAG3 protein as bait, we fished out and identified the cytosolic chaperonin CCT, a new unreported BAG3 partner. The interaction between BAG3 and CCT was confirmed and characterized by co-immunoprecipitation experiments and surface plasmon resonance techniques. Furthermore, our analyses showed a slower CCT association and a faster dissociation with a truncated form of BAG3 containing the BAG domain, thus indicating that other protein regions are essential for a high-affinity interaction. ATP or ADP does not seem to significantly influence the chaperonin binding to BAG3 protein. On the other hand, our experiments showed that BAG3 silencing by small interfering RNA slowed down cell migration and influence the availability of correctly folded monomeric actin, analyzed by DNAse I binding assays and latrunculin A depolymerization studies. To our knowledge, this is the first report showing abiologically relevant interaction between the chaperonin CCT and BAG3 protein, thus suggesting interesting involvement in the folding processes regulated by CCT

Respiratory DC use IFITM3 to avoid direct viral infection and safeguard virus-specific CD8+ T cell priming

10.1371/journal.pone.0143539PLoS ONE1011e014353