Characterizing methyl-bearing side chain contacts and dynamics mediating amyloid ? protofibril interactions using ¹³C(methyl)-DEST and lifetime line broadening.

ABSTRACT: Many details pertaining to the formation and interactions of protein aggregates associated with neurodegenerative diseases are invisible to conventional biophysical techniques. We recently introduced (15)N dark-state exchange saturation transfer (DEST) and (15)N lifetime line-broadening to study solution backbone dynamics and position-specific binding probabilities for amyloid?? (A?) monomers in exchange with large (2-80?MDa) protofibrillar A? aggregates. Here we use (13)C(methyl)DEST and lifetime line-broadening to probe the interactions and dynamics of methyl-bearing side chains in the A?-protofibril-bound state. We show that all methyl groups of A?40 populate direct-contact bound states with a very fast effective transverse relaxation rate, indicative of side-chain-mediated direct binding to the protofibril surface. The data are consistent with position-specific enhancements of (13)C(methyl)-R?(tethered) values in tethered states, providing further insights into the structural ensemble of the protofibril-bound state.

SUBMITTER: Fawzi NL 

PROVIDER: S-EPMC4539159 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature