title: High-resolution conformation and backbone dynamics of a soluble aggregate of apomyoglobin119.
abstract: 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 apomyoglobin(119) (apoMb(119)), generated upon truncating the residues corresponding to the C-terminal helix of sperm whale apomyoglobin. The secondary structure and backbone dynamics of apoMb(119), 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 apoMb(119) 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 apoMb(119)'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 apoMb(119)'s aggregation.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin.
authors.forename: Senapathy
authors.initials: S
authors.lastname: Rajagopalan
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin.
authors.forename: Neşe
authors.initials: N
authors.lastname: Kurt
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin. Electronic address: cavagnero@chem.wisc.edu.
authors.forename: Silvia
authors.initials: S
authors.lastname: Cavagnero
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001059:Apoproteins / Q000737:chemistry*; D001665:Binding Sites; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009211:Myoglobin / Q000737:chemistry*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012995:Solubility; D050661:Sperm Whale
chemical_list: D001059:Apoproteins; D009211:Myoglobin; C010857:apomyoglobin; D000251:Adenosine Triphosphatases