Manganese Enhances Prion Protein Survival in Model Soils and Increases Prion Infectivity to Cells

Prion diseases are considered to be transmissible. The existence of sporadic forms of prion diseases such as scrapie implies an environmental source for the infectious agent. This would suggest that under certain conditions the prion protein, the accepted agent of transmission, can survive in the environment. We have developed a novel technique to extract the prion protein from soil matrices. Previous studies have suggested that environmental manganese is a possible risk factor for prion diseases. We have shown that exposure to manganese is a soil matrix causes a dramatic increase in prion protein survival (∼10 fold) over a two year period. We have also shown that manganese increases infectivity of mouse passaged scrapie to culture cells by 2 logs. These results clearly verify that manganese is a risk factor for both the survival of the infectious agent in the environment and its transmissibility

Conformational Plasticity of proNGF

Nerve Growth Factor is an essential protein that supports neuronal survival during development and influences neuronal function throughout adulthood, both in the central and peripheral nervous system. The unprocessed precursor of NGF, proNGF, seems to be endowed with biological functions distinct from those of the mature protein, such as chaperone-like activities and apoptotic and/or neurotrophic properties. We have previously suggested, based on Small Angle X-ray Scattering data, that recombinant murine proNGF has features typical of an intrinsically unfolded protein. Using complementary biophysical techniques, we show here new evidence that clarifies and widens this hypothesis through a detailed comparison of the structural properties of NGF and proNGF. Our data provide direct information about the dynamic properties of the pro-peptide and indicate that proNGF assumes in solution a compact globular conformation. The N-terminal pro-peptide extension influences the chemical environment of the mature protein and protects the protein from proteolytic digestion. Accordingly, we observe that unfolding of proNGF involves a two-steps mechanism. The distinct structural properties of proNGF as compared to NGF agree with and rationalise a different functional role of the precursor

The mechanisms of humic substances self-assembly with biological molecules: The case study of the prion protein

Humic substances (HS) are the largest constituent of soil organic matter and are considered as a key component of the terrestrial ecosystem. HS may facilitate the transport of organic and inorganic molecules, as well as the sorption interactions with environmentally relevant proteins such as prions. Prions enter the environment through shedding from live hosts, facilitating a sustained incidence of animal prion diseases such as Chronic Wasting Disease and scrapie in cervid and ovine populations, respectively. Changes in prion structure upon environmental exposure may be significant as they can affect prion infectivity and disease pathology. Despite its relevance, the mechanisms of prion interaction with HS are still not completely understood. The goal of this work is to advance a structural-level picture of the encapsulation of recombinant, non-infectious, prion protein (PrP) into different natural HS. We observed that PrP precipitation upon addition of HS is mainly driven by a mechanism of “salting-out” whereby PrP molecules are rapidly removed from the solution and aggregate in insoluble adducts with humic molecules. Importantly, this process does not alter the protein folding since insoluble PrP retains its α-helical content when in complex with HS. The observed ability of HS to promote PrP insolubilization without altering its secondary structure may have potential relevance in the context of “prion ecology”. These results suggest that soil organic matter interacts with prions possibly without altering the protein structures. This may facilitate prions preservation from biotic and abiotic degradation leading to their accumulation in the environment

SUR LA MESURE DIRECTE DU DÉBIT DE FILTRATION CHEZ LES MOLLUSQUES LAMELLIBRANCHES

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Conformational changes of enzymes adsorbed at liquid- solid interface: Relevance to enzymatic activity

International audienceFTIR-ATR spectroscopy has been used to study in-situ adsorption of enzymes at water/solid interfaces so as to better understand how conformational changes may monitor enzymatic activity. As the adsorption process depends on hydrophobic and electrostatic interactions, conformational changes have been studied as a function of the nature of the adsorbing substrates: hydrophobic or hydrophilic character. Adsorption kinetics of two examples of serine enzyme, -chymotrypsin (-chym) and Humicola lanuginosa lipase (HLL), have been studied. Both secondary structure and solvation of the adsorbed enzymes have been compared to the dissolved enzymes. While the positively charged -chym was adsorbed on a negatively charged hydrophilic support with minor structural changes, the negatively charged lipase has no affinity for a similar support. Both enzymes were strongly retained on the hydrophobic support. The secondary and tertiary structures of the -chym adsorbed on hydrophobic support were strongly altered, in correlation with the inhibition of enzymatic hydrolysis. The specific solvation obtained for the adsorbed HLL is consistent with the existence of the open conformer, in relation with the enhanced enzymatic activity at the water/hydrophobic interface

SUR LA MESURE DIRECTE DU DÉBIT DE FILTRATION CHEZ LES MOLLUSQUES LAMELLIBRANCHES

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Conformational changes of bovine serum albumin induced by adsorption on different clay surfaces: FTIR analysis

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Conformational Changes of Bovine Serum Albumin Induced by Adsorption on Different Clay Surfaces: FTIR Analysis

International audienceInteractions between proteins and clays perturb biological activity in ecosystems, particularly soil extracellular enzyme activity. The pH dependence of hydrophobic, hydrophilic, and electrostatic interactions on the adsorption of bovine serum albumin (BSA) is studied. BSA secondary structures and hydration are revealed from computation of the Amide I and II FTIR absorption profiles. The influence of ionization of Asp, Glu, and His side chains on the adsorp-tion processes is deduced from correlation between p 2 H dependent carboxylic/carboxylate ratio and Amide band profiles. We quantify p 2 H dependent internal and external structural unfolding for BSA adsorbed on montmorillonite, which is an electronegative phyllosil-icate. Adsorption on talc, a hydrophobic surface, is less denaturing. The results emphasize the importance of electrostatic interactions in both adsorption processes. In the first case, charged side chains directly influence BSA adsorption that generate the structural transition. In the second case, the forces that attract hydrophobic side chains toward the protein-clay interface are large enough to distort peripheral amphiphilic helical domains. The resulting local unfolding displaces enough internal ionized side chains to prevent them from establishing salt bridges as for BSA native structure in solution. On montmorillonite, a particular feature is a higher protonation of the Asp and Glu side chains of the adsorbed BSA than in solution, which decreases coulombic repulsion

Chymotrypsin adsorption on Montmorillonite: Enzymatic activity and kinetic FTIR structural analysis

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