1,721,015 research outputs found
Structural Studies of Prion Proteins and Prions
No full textPrion diseases are a group of fatal and incurable neurodegenerative disorders of mammals. They uniquely manifest as sporadic, genetic, and infectious maladies. The agent responsible for prion diseases is the prion. A prion is defined as a proteinaceous infectious particle, which is solely constituted by an alternately folded form of the prion protein (PrP) (Prusiner 1982).
In diseased animals and humans, PrP exists in two forms, the physiological, cel- lular form of PrP, PrPC, and the pathological prion form denoted as PrPSc. The mech- anism whereby nascent PrPSc is generated is currently unknown. Structural studies of either isoform are of great importance for understanding the biology of prion diseases since they may clarify the molecular mechanisms responsible for these pathologies. In this chapter, we present an overview of the studies into PrPC as well as structures of prions
Hidden β-γ Dehydrogenation Products in Long-Chain Fatty Acid Oxidation Unveiled by NMR: Implications on Lipid Metabolism
Full text linkWe present a comprehensive analysis of the initial α,β-dehydrogenation step in long-chain fatty acid β-oxidation (FAO). We focused on palmitoyl-CoA oxidized by two mitochondrial acyl-CoA dehydrogenases, very-long-chain acyl-CoA dehydrogenase (VLCAD) and acyl-CoA dehydrogenase family member 9 (ACAD9), both implicated in mitochondrial diseases. By combining MS and NMR, we identified the (2E)-hexadecenoyl-CoA as the expected α-β-dehydrogenation product and also the E and Z stereoisomers of 3-hexadecenoyl-CoA: a “γ-oxidation” product. This finding reveals an alternative catalytic pathway in mitochondrial FAO, suggesting a potential regulatory role for ACAD9 and VLCAD during fatty acid metabolism
Synthetic prions
No full textPrion diseases are invariably fatal neurodegenerative disorders affecting humans and many mammals. Here, we will discuss the current understanding of prion biology and the molecular biology of this group of illnesses. We introduce several aspects of prion biology, from the primary structure of the cellular form of the prion protein, PrPC, to the conformational changes that occur during the conversion to the pathological form, PrPSc. In particular, we provide recent developments in our understanding of the molecular determinants of prion infectivity. We present in detail the discovery of synthetic mammalian prions and the implications that such findings may have for the future of prion research. © 2012 by Nova Science Publishers, Inc. All rights reserved
NMR studies of human prion proteins with inherited mutations
No full textPrion diseases are fatal neurodegenerative disorders caused by an aberrant accumulation of the misfolded cellular prion protein (PrPC) conformer, denoted as infectious scrapie isoform or PrPSc. Our understanding of the mechanisms by which mutations cause disease remains limited. In this work results of recent high-resolution NMR structural studies on human prion protein variants carrying pathological mutations are presented
Soil humic substances hinder the propagation of prions
Full text linkPrions are infectious pathogens causing fatal neurodegenerative disorders, known as transmissible spongiform encephalopathies (TSEs), or prion diseases, which affect different mammalian species. TSEs include scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle, chronic wasting disease (CWD) in mule deer, elk, and moose (cervids), and Creutzfeldt-Jakob disease (CJD) in humans. The prominent, if not only, component of prions is a misfolded conformer (PrPSc) of a constitutive sialoglycoprotein, the cellular prion protein (PrPC). A notable feature of prion diseases is horizontal transmission between grazing animals, implying that contaminated soil may serve to propagate the disease. In this respect, it has been reported that grazing animals ingest from tens to hundreds grams of soil per day, either incidentally through the diet, or deliberately in answering salt needs, and that mule deer can develop CWD after grazing in locations that previously housed infected ..
Recognition Mechanisms between a Nanobody and Disordered Epitopes of the Human Prion Protein: An Integrative Molecular Dynamics Study
Full text link: Immunotherapy using antibodies to target the aggregation of flexible proteins holds promise for therapeutic interventions in neurodegenerative diseases caused by protein misfolding. Prions or PrPSc, the causal agents of transmissible spongiform encephalopathies (TSE), represent a model target for immunotherapies as TSE are prototypical protein misfolding diseases. The X-ray crystal structure of the wild-type (WT) human prion protein (HuPrP) bound to a camelid antibody fragment, denoted as Nanobody 484 (Nb484), has been previously solved. Nb484 was found to inhibit prion aggregation in vitro through a unique mechanism of structural stabilization of two disordered epitopes, that is, the palindromic motif (residues 113-120) and the β2-α2 loop region (residues 164-185). The study of the structural basis for antibody recognition of flexible proteins requires appropriate sampling techniques for the identification of conformational states occurring in disordered epitopes. To elucidate the Nb484-HuPrP recognition mechanisms, here we applied molecular dynamics (MD) simulations complemented with available NMR and X-ray crystallography data collected on the WT HuPrP to describe the conformational spaces occurring on HuPrP prior to Nb484 binding. We observe the experimentally determined binding competent conformations within the ensembles of pre-existing conformational states in solution before binding. We also described the Nb484 recognition mechanisms in two HuPrP carrying a polymorphism (E219K) and a TSE-causing mutation (V210I). Our hybrid approaches allow the identification of dynamic conformational landscapes existing on HuPrP and highly characterized by molecular disorder to identify physiologically relevant and druggable transitions
A single point mutation, a way to prion disease?
No full textPrion diseases or Transmissible Spongiform Encephalopathies (TSE) are a group of fatal neurodegenerative illnesses affecting humans and animals. They are classified into sporadic, genetic and infectious forms. Genetic prion diseases are caused by mutations in the human prion protein gene and include Gerstmann-Straussler-Scheinker (GSS) syndrome, Fatal Familial Insomnia and genetic Creutzfeldt-Jakob disease (CJD). Approximately 10-15% of all TSE cases in humans are associated with mutations. The development of TSEs is associated with the conversion of the cellular prion protein (PrPC) into a misfolded, pathogenic isoform (PrPSc). Our recent NMR studies were focused on structural characterization of different truncated recombinant human (Hu) PrPs carrying the pathological Q212P (90-231, M129) and V210I(90-231, M129) mutations, and protective E219K (90-231, M129) polymorphism. While Q212P mutation is linked to GSS, the V210I mutation is linked to genetic CJD. The naturally occurring E219K polymorphism in the HuPrP is considered to protect against sCJD. We have demonstrated that the determined structures of variants consist of unstructured N-terminal part (residues 90-124) and well defined C-terminal domain (residues 125-228). Analysis and comparison with the structure of the WT HuPrP revealed that although structures share similar global fold, mutations introduces several local structural differences. The observed differences are mostly clustered at the alpha2-alpha3 inter-helical interface and in the beta2-alpha2 loop region. The determined NMR structures offer new insights on the earliest events of the pathogenic conversion process and could be used for the development of antiprion drugs. More recently we have determined solution state structures of V210I (90-231, M129) pathogenic mutation at two different conditions with pH 5.5 and 7.2. The detailed comparison of three-dimensional structures of HuPrP(V210I) at two different pH values revealed that interactions among secondary structure elements have a higher degree of structural ordering under neutral pH conditions, thus implying that spontaneous misfolding of PrPC may occur under acidic-pH conditions in endosomal compartments
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