Protein aggregation

The objectives of the thesis: The aim of the studies is to gain fundamental understanding of the role of hydrophobic and polar sequence on folding mechanism of proteins and aggregation of peptides

33p xacxuoc4321 09-07-2019 43 4   Download

Heterologous expression of the extracellular domains (ECDs) of the nicotinic acetylcholine receptor (AChR) subunits may give large amounts of proteins for studying the functional and spatial characteristics of their ligand-binding sites. The ECD of the a7 subunit of the homo-oligomeric a7 neuronal AChR appears to be a more suitable object than the ECDs of other heteromeric neuronal or muscle-type AChRs. The rat a7 ECDs (amino-acid residues  1–210) were recently expressed in Escherichia coli as fusion proteins with maltose-binding protein...

9p system191 01-06-2013 39 3   Download

The phenomenon of the transformation of proteins into amyloid-fibrils is of interest, firstly, because it is closely connected to the so-called conformational diseases, many of which are hitherto incurable, and secondly, because it remains to be explained in physical terms (energetically and structurally). The process leads to fibrous aggregates in the form of extracellular amyloid plaques, neuro-fibrillary tangles and other intracytoplasmic or intranuclear inclusions.

10p research12 01-06-2013 33 4   Download

The Na + /H + exchanger is a ubiquitous membrane protein of bacteria, plants and mammals. The first isoform discov-ered (NHE1) is present on the mammalian plasma mem-brane and transports oneH + out of cells inexchange for one extracellular Na + . With solubilization in standard SDS/ PAGE buffer, this protein had a high tendency to aggregate when subjected to elevated temperature. The aggregates were stable and did not dissociate in high concentrations of SDSor 2-mercaptoethanol.

9p research12 29-04-2013 46 3   Download

Here we show, for the ®rst time, thein vitro formation of ®lamentous aggregates of phosphorylated tau protein in SH-SY5Y human neuroblastoma cells. The formation of suchaberrant aggregates, similar to thoseoccurringinvivoin Alzheimer's disease and other tauopathies, requires okadaic acid, a phosphatase inhibitor, to increase the level of phos-phorylated tau, and hydroxynonenal, a product of oxidative stress that selectively adducts and modi®es phosphorylated tau.

6p research12 29-04-2013 31 2   Download

We investigated the effect of nitric oxide (NO) donors on the activities of annexin II tetramer (AIIt), a member of the Ca 2+ -dependent phospholipid-binding protein family. Incubation of purified AIIt with S-nitrosoglutathione (GSNO) led to the inhibition of AIIt-mediated liposome aggregation. This effect was dose-dependent with an IC50 of approximately 100lM. Sodium nitroprusside, another NO donor also inhibited AIIt-mediated liposome aggregation, whereas reduced glutathione, nitrate, or nitrite had no effects. ...

10p research12 23-04-2013 29 4   Download

Hemolin, a plasma protein from lepidopteran insects, is composed of four immunoglobulin domains. Its synthesis is induced by microbial challenge. We investigated the biological functions of hemolin inManduca sexta.It was found to bind to the surface of bacteria and yeast, and caused these micro-organisms to aggregate. Hemolin was demonstrated to bind to lipopolysaccharide (LPS) from Gram-negativebacteriaand to lipoteichoic acid fromGram-positive bacteria.

8p research12 23-04-2013 38 2   Download

Amyloid protein (Ab1–40) aggregation and conformation was examined using native and sodium dodecyl sulfate/ polyacrylamide gel electrophoresis,and the results com-pared with those obtained by atomic force microscopy, and with Congo red binding,sedimentation and turbidity assays. The amount of Ab aggregation measured was different,depending upon the method used. Incubation for 15 min at pH 5.0 or in the presence of Fe 2+ ,Cu 2+ or Zn 2+ did not alter the level of Aboligomers observed on SDS and native gels....

12p tumor12 20-04-2013 42 4   Download

Mammalian translation initiation factor 3 (eIF3) is a multisubunit complex containingat least 12 subunitswithan apparent aggregate mass of
700 kDa.eIF3 binds to the 40S ribosomal subunit, promotes the binding of methionyl-tRNA i and mRNA, and interacts with several other initi-ation factors to form the 40S initiation complex.Human cDNAs encoding 11 of the 12 subunits have been isolated previously; here we report the cloning and characterization of a twelfth subunit, a 28-kDa protein named eIF3k.Evi-dence that eIF3k is present in the eIF3 complex was obtained....

7p tumor12 20-04-2013 33 3   Download

a-Crystallin, a molecular chaperone and lens structural protein protects soluble enzymes against heat-induced aggregation and inactivation by a variety of molecules. In this study we investigated the chaperone function ofa-crys-tallininamorephysiological systeminwhicha-crystallinwas incorporated into red cell
ghosts. Its ability to protect the intrinsic membrane protein Na/K-ATPase from external stresses was studied. Red cell ghosts were created by lysing the red cells and removing cytoplasmic contents by size-exclusion chromatography. ...

7p fptmusic 16-04-2013 49 2   Download

Recently, a new protein containing a disintegrin domain, alternagin-C (Alt-C), was purified fromBothrops alternatus venom. Unlike other disintegrins, in Alt-C an ECD amino acid motif takes the place of the RGD sequence. Most dis-integrins contain an RGD/KGD sequence and are very potent inhibitors of platelet aggregation, as well as other cell interactions with the extracellular matrix, including tumor cell metastasis and angiogenesis. The present study investi-gated the effects of Alt-C on human neutrophil chemotaxis in vitro and the activation of integrin-mediated pathways....

10p fptmusic 12-04-2013 37 2   Download

Proteins tend to form inactive aggregates at high tempera-tures. We show that polyamines, which have a relatively simple structure as oligoamids, effectively prevent thermal inactivation and aggregation of hen egg lysozyme. In the presence of additives, including arginine and guanidine (100 mM), more than 30% of 0.2 mgÆmL )1 lysozyme in sodium phosphate buffer (pH 6.5) formed insoluble aggre-gates by heat treatment (98
C for 30 min). 1

8p fptmusic 12-04-2013 44 3   Download

Misfolded proteins, aggregates, and inclusion bodies are hall-marks of the cytopathology of neurodegenerative disorders including Huntington’s disease, Amyotropic lateral sclerosis, Parkinson’s disease, Prion diseases, and Alzheimer’s disease. The appearance of proteins with altered folded states is regula-ted by the protein folding quality control machinery and age-dependent. We have identified an unexpected molecular link between metabolic state, accumulation of damaged proteins, the heat-shock response and chaperones, and longevity....

61p fptmusic 11-04-2013 46 5   Download

Protein aggregation is central to most neurodegenerative diseases, as shown by familial case studies and by animal models. A modified ‘amyloid cas-cade’ hypothesis for Alzheimer’s disease states that prefibrillar oligomers, also called amyloid-b-derived diffusible ligands or globular oligomers, are the responsible toxic agent. It has been proposed that these oligomeric spe-cies, as shown for amyloid-b, b2 -microglobulin or prion fragments, exert toxicity by forming pores in membranes, initiating a cascade of detrimental events for the cell. ...

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Small heat shock proteins (sHSPs) function as molecular chaperones, pre-venting stress induced aggregation of partially denatured proteins and pro-moting their return to native conformations when favorable conditions pertain. Sequence similarity between sHSPs resides predominately in an internal stretch of residues termed the a-crystallin domain, a region usually flanked by two extensions.

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Recently, a novel plaque-associated protein, collagenous Alzheimer amy-loid plaque component (CLAC), was identified in brains from patients with Alzheimer’s disease. CLAC is derived from a type II transmembrane colla-gen precursor protein, termed CLAC-P (collagen XXV). The biological function and the contribution of CLAC to the pathogenesis of Alzheimer’s disease and plaque formation are unknown.

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a-lactalbumin (LA) in its molten globule (MG) state at low pH forms amyloid fibrils. Here, we have studied the aggregation propensities of LA derivatives characterized by a single peptide bond fission (1–40⁄41–123, named Th1-LA) or a deletion of a chain segment of 12 amino acid resi-dues located at the level of the b-subdomain of the native protein (1– 40⁄53–123, named desb-LA). We have also compared the early stages of the aggregation process of these LA derivatives with those of intact LA....

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In the majority of hypophosphatasia patients, reductions in the serum lev-els of alkaline phosphatase activity are caused by various missense muta-tions in the tissue-nonspecific alkaline phosphatase (TNSALP) gene. A unique frame-shift mutation due to a deletion of T at cDNA number 1559 [TNSALP (1559delT)] has been reported only in Japanese patients with high allele frequency.

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A yeast model was generated to study the mechanisms and phenotypical repercussions of expression of a-synuclein as well as the coexpression of protein tau. The data show that aggregation ofa-synuclein is a nucleation– elongation process initiated at the plasma membrane. Aggregation is con-sistently enhanced by dimethyl sulfoxide, which is known to increase the level of phospholipids and membranes in yeast cells.

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a-Crystallin is the principal lens protein which, in addition to its structural role, also acts as a molecular chaperone, to prevent aggregation and preci-pitation of other lens proteins. One of its two subunits,aB-crystallin, is also expressed in many nonlenticular tissues, and a natural missense muta-tion, R120G, has been associated with cataract and desmin-related myopa-

14p awards 05-04-2013 44 2   Download