Elucidating the multi-targeted anti-amyloid activity and enhanced islet amyloid polypeptide binding of ß-wrapins.

ABSTRACT

ß-wrapins are engineered binding proteins stabilizing the ß-hairpin conformations of amyloidogenic proteins islet amyloid polypeptide (IAPP), amyloid-ß, and α-synuclein, thus inhibiting their amyloid propensity. Here, we use computational and experimental methods to investigate the molecular recognition of IAPP by ß-wrapins. We show that the multi-targeted, IAPP, amyloid-ß, and α-synuclein, binding properties of ß-wrapins originate mainly from optimized interactions between ß-wrapin residues and sets of residues in the three amyloidogenic proteins with similar physicochemical properties. Our results suggest that IAPP is a comparatively promiscuous ß-wrapin target, probably due to the low number of charged residues in the IAPP ß-hairpin motif. The sub-micromolar affinity of ß-wrapin HI18, specifically selected against IAPP, is achieved in part by salt-bridge formation between HI18 residue Glu10 and the IAPP N-terminal residue Lys1, both located in the flexible N-termini of the interacting proteins. Our findings provide insights towards developing novel protein-based single- or multi-targeted therapeutics.