The post-translational incorporation of arginine into a beta-amyloid peptide increases the probability of alpha-helix formation

THE beta-amyloid peptide (beta AP(1-40)) inhibited the in vitro post-translational incorporation of [C-14]arginine at the N-terminus of brain soluble proteins and was labelled by the incorporation of [C-14]arginine. Addition of arginine at the N-terminal position of beta AP(1-10) is predicted to increase the probability of an alpha-helix structure being formed on the first residues with a higher hydrophilic characteristic, increasing the possibility of these residues being exposed to the aqueous environment. Unmodified beta AP(1-40) has a low alpha-helix content and a higher probability of beta-turn formation. Accumulation of beta AP(1-40) in Alzheimer's disease may therefore be due to a reduced arginylation reaction and consequently to a decrease in its normal degradation by the ubiquitin pathway.