A Combinatorial NMR and EPR Approach for Evaluating the Structural Ensemble of Partially Folded Proteins

• DOI: 10.1021/ja100646t
• Publication Date: 2010-06-04T17:39:23Z
• Authors: Jampani Nageswara...; Christine C. Jao; Balachandra G. Hegde; Ralf Langen; Tobias S. Ulmer
• Keywords: Antiparallel (mathematics); Site-directed spin labeling

Partially folded proteins, characterized as exhibiting secondary structure elements with loose or absent tertiary contacts, represent important intermediates in both physiological protein folding and pathological misfolding. To aid the characterization of structural state(s) such a novel calculation scheme is presented that combines restraints derived from pulsed EPR NMR spectroscopy. The methodology established for α-synuclein (αS), which exhibits characteristics partially when bound to micelle detergent sodium lauroyl sarcosinate (SLAS). By combining 18 EPR-derived interelectron spin label distance distributions NMR-based definitions bond vector restraints, distances were correlated set theoretical ensemble basis populations was calculated. A minimal structures, representing state SLAS-bound αS, subsequently by back-calculating distributions. surprising variety well-defined protein−micelle interactions thus revealed engulfed two differently arranged antiparallel αS helices. further provided population ratios between dominant states, whereas limitation obtainable resolution arose flexibility residual uncertainties definitions. advance understanding interactions, present study concludes showing that, marked contrast stability, helix dynamics correlate degree protein-induced departures free dimensions.