RNA-protein complexes have emerged as central players in numerous key cellular processes with significant relevance in health and disease. To further deepen our knowledge of RNA-binding proteins (RBPs), multiple proteome-wide strategies have been developed to identify RBPs in different species leading to a large number of studies contributing experimentally identified as well as predicted RBP candidate catalogs. However, the rapid evolution of the field led to an accumulation of isolated datasets, hampering the access and comparison of their valuable content.
View Article and Find Full Text PDFThe adaptor protein Miranda plays a pivotal role in the asymmetric cell division of neuroblasts by asymmetrically segregating key differentiation factors. Miranda localization requires Myosin VI and Myosin II. The apical-then-basal localization pattern of Miranda detected in fixed tissue, and the localization defects in embryos lacking Myosin VI, suggest that Miranda is transported to the basal pole as a Myosin VI cargo.
View Article and Find Full Text PDFSolvational perturbations, accomplished by the addition of the three model cosolvents glycerol, ethanol and trifluoroethanol, exert pronounced and diversified effects on the unfolding, non-native assembly and fibril formation of the amyloidogenic protein insulin. Fluorescence, CD and UV-spectroscopic methods as well as atomic force microscopy imaging have been employed to reveal distinct structural and kinetic features upon the aggregation of insulin under different solvational perturbations, which ultimately manifest in morphological variations of mature aggregates and fibrils. In particular, fluorescence anisotropy studies proved to be very valuable in characterizing the corresponding aggregation nuclei.
View Article and Find Full Text PDFA model cosolvent, ethanol, has profound and diversified effects on the amyloidogenic self-assembly of insulin, yielding spectroscopically and morphologically distinguishable forms of beta-aggregates. The alcohol reduces hydrodynamic radii of insulin molecules, decreases enthalpic costs associated with aggregation-prone intermediate states, and accelerates the aggregation itself. Increasing the concentration of the cosolvent promotes curved, amorphous, and finally donut-shaped forms.
View Article and Find Full Text PDFIn the presence of ethanol, insulin forms amyloid morphologically distinct from the ambient specimen. Due to stability of fibrils and the autocatalytic character of the process, the two amyloid templates, when seeded, replicate the initial morphologies (and inter-beta-strand hydrogen bonding patterns) regardless of the environmental biases, such as the cosolvent presence. Such "templated memory" effect is advantageous in synthesizing structurally uniform protein nanofibrils under conditions favoring alternative "wild" forms.
View Article and Find Full Text PDFAs the application of high-resolution atomic force microscopy (AFM) has led us recently to the discovery of a unique pressure-induced circular amyloid, we used the same approach to examine morphological events accompanying insulin aggregation under ambient conditions. This study presents the multistage, hierarchical character of the spontaneous fibrillation of insulin at low pH and at 60 and 70 degrees C, and-due to the marked enhancement of image resolution achieved-brings new clues as to the fibrils' ultrastructure and mechanisms of its assembly. Specifically, focusing on the prefibrillar amorphous aggregates occurring 30 s after elevating temperature to the nucleation-enhancing 60 degrees C, revealed the tendency of the globule-shaped oligomers to queue and assembly into elongated forms.
View Article and Find Full Text PDFThe presence of 20% (v/v) ethanol triggers growth of insulin amyloid with distinct infrared spectroscopic features, compared with the fibrils obtained under ambient conditions. Here we report that the two insulin amyloid types behave in the prion strain-like manner regarding seeding specificity and ability of the self-propagating conformational template to overrule unfavorable environmental factors and maintain the initial folding pattern. The type of the original seed has been shown to prevail over cosolvent effects and determines spectral position and width of the amide I' infrared band of the heterogeneously seeded amyloid.
View Article and Find Full Text PDFAmyloids, initially associated with certain degenerative diseases, and recently with the prions and prion-based inheritance in yeasts, are linearly-ordered beta-sheet-rich protein aggregates, presently thought to represent a rather common generic trait of proteins as polymers. Regardless of genetic origins and properties of precursor protein molecules, amyloids share many physicochemical properties, including the linear fibrillar morphology. Here, we show that under high hydrostatic pressure insulin forms amyloids of a unique circular morphology.
View Article and Find Full Text PDFThe interaction of left- and right-handed polylysine chains (poly(D-lysine) and poly(L-lysine)) results in a dramatic increase in the propensity to form aggregated beta-sheet structure (and amyloid-like fibrils), which is reflected by an approximately 15 degrees C decrease of temperature of the alpha-helix-to-beta-sheet transition. While a relative volume expansion of 13-19 mL x mol(-1) accompanies the alpha-to-beta-transition in a single enantiomer, this does not hold true for the mixture, which, along with substantially more negative heat capacity changes, points to a lower solvent-entropy cost of the transition as the possible thermodynamic driving force of the diastereomeric aggregation. The underlying solvational mechanism may be one of the decisive factors responsible for the spontaneous protein aggregation in vivo and, as such, may shed new light on the molecular basis of amyloid-associated diseases.
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