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Amyloid fibrils found in plaques in Alzheimer's disease (AD) brains are composed of amyloid-β peptides. Oligomeric amyloid-β 1-42 (Aβ42) is thought to play a critical role in neurodegeneration in AD. Here, we determine how size and conformation affect neurotoxicity and internalisation of Aβ42 assemblies using biophysical methods, immunoblotting, toxicity assays and live-cell imaging. We report significant cytotoxicity of Aβ42 oligomers and their internalisation into neurons. In contrast, Aβ42 fibrils show reduced internalisation and no toxicity. Sonicating Aβ42 fibrils generates species similar in size to oligomers but remains nontoxic. The results suggest that Aβ42 oligomers have unique properties that underlie their neurotoxic potential. Furthermore, we show that incubating cells with Aβ42 oligomers for 24 h is sufficient to trigger irreversible neurotoxicity., (© 2020 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

β-amyloid 1-42 (Aβ1-42) is a self-assembling peptide that goes through many conformational and morphological changes before forming the fibrils that are deposited in extracellular plaques characteristic of Alzheimer's disease. The link between Aβ1-42 structure and toxicity is of major interest, in particular, the neurotoxic potential of oligomeric species. Many studies utilise reversed (Aβ42-1) and scrambled (AβS) forms of amyloid-β as control peptides. Here, using circular dichroism, thioflavin T fluorescence and transmission electron microscopy, we reveal that both control peptides self-assemble to form fibres within 24 h. However, oligomeric Aβ reduces cell survival of hippocampal neurons, while Aβ42-1 and Aβs have reduced effect on cellular health, which may arise from their ability to assemble rapidly to form protofibrils and fibrils., (© 2017 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Soluble Amyloid-beta (Aβ) oligomers are a source of cytotoxicity in Alzheimer's disease (AD). The toxicity of Aβ oligomers may arise from their ability to interact with and disrupt cellular membranes mediated by GM1 ganglioside receptors within these membranes. Therefore, inhibition of Aβ-membrane interactions could provide a means of preventing the toxicity associated with Aβ. Here, using Surface Plasmon field-enhanced Fluorescence Spectroscopy, we determine that the lanthanide, Europium III chloride (Eu(3+)), strongly binds to GM1 ganglioside-containing membranes and prevents the interaction with Aβ42 leading to a loss of the peptides ability to cause membrane permeation. Here we discuss the molecular mechanism by which Eu(3+) inhibits Aβ42-membrane interactions and this may lead to protection of membrane integrity against Aβ42 induced toxicity., (Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.)

An expression and mutagenesis system for the E. coli Class II fructose-1,6-bisphosphate aldolase has been created by modification of the vector pKfda (Biochem. J. 257 (1989) 529-534). Large amounts of Class II aldolase (about 1 g/l in crude extracts), with properties consistent with those previously reported for the naturally occurring enzyme (Biochem. J. 169 (1978) 633-641) are obtained. The enzyme contains 2 zinc ions per enzyme dimer. We have investigated the nature of the zinc-binding site of the enzyme by site-directed mutagenesis. His-108, His-111, Cys-112 and His-142 were identified as possible zinc-binding ligands by sequence alignments and comparisons with other known zinc-containing enzymes. Mutation of these residues identified His-108 and His-111 as two of the ligands directly responsible for the tight binding of zinc. Mutation of the other two residues results in only a small effect on the amount of zinc bound per monomer and a corresponding change in specific activity. These residues are, therefore, unlikely to be directly involved in zinc binding, but may be indirectly involved in some manner in the zinc-binding environment.