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

The beta-amyloid peptide (beta AP1-40) inhibited the in vitro post-translational incorporation of [14C]arginine at the N-terminus of brain soluble proteins and was labelled by the incorporation of [14C]arginine. Addition of arginine at the N-terminal position of beta AP1-40 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 AP1-40 has a low alpha-helix content and a higher probability of beta-turn formation. Accumulation of beta AP1-40 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.