High-Resolution Conformation and Backbone Dynamics of a Soluble Aggregate of Apomyoglobin119

• Published in: Biophysical Journal
• Main Authors: Rajagopalan, Senapathy, Kurt, Neşe, Cavagnero, Silvia
• Format: Text
• Language: English
• Published: The Biophysical Society 2011
• Subjects: Protein; Sperm whale
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3030155; http://www.ncbi.nlm.nih.gov/pubmed/21281590; https://doi.org/10.1016/j.bpj.2010.12.3722

The structure and dynamics of soluble misfolded aggregates are poorly understood, despite their importance in protein science and disease. Water-soluble self-associated species that do not become insoluble over time are invaluable tools for high-resolution conformational studies aimed at dissecting the determinants of self-association. Here, we characterize the soluble model aggregate apomyoglobin119 (apoMb119), generated upon truncating the residues corresponding to the C-terminal helix of sperm whale apomyoglobin. The secondary structure and backbone dynamics of apoMb119, determined by multidimensional NMR at pH 6.0, reveal the presence of an N-terminal slow-tumbling core and a highly disordered flexible C-terminus displaying residual helicity and large-amplitude backbone motions on the picosecond-to-nanosecond timescale. The backbone of the apoMb119 aggregate assumes progressively increased mobility as residues get further removed from the nonpolar core and closer to the more hydrophilic C-terminal end. This structural motif establishes a useful paradigm for the topology of soluble misfolded protein aggregates in aqueous solution in the absence of stabilizing additives. The partially helical and flexible C-terminus of apoMb119's aggregate is in interesting contrast with the amyloid-related globulomers, which display dangling ends rich in β-strand. Finally, we investigate how a molecular chaperone, the substrate-binding domain of DnaK, interferes with apoMb119's aggregation.