title: Coalescence of spherical beads of retro-HSP12.6 into linear and ring-shaped amyloid nanofibers.
abstract: The sequence-reversed form of a small heat shock protein, HSP12.6 (retro-HSP12.6), has been reported to fold and assemble into structured tetramers in aqueous solution. Upon raising the protein concentration to ~1.0-1.5 mg/ml, tetrameric retro-HSP12.6 is known to display a tendency to associate further into spherical beads of 18-20 nm in diameter containing folded protein subunits. Here we report that storage of this protein at low temperatures leads to further association of the beaded structures into linear and ring-shaped amyloid nanofibers of 18-20 nm in diameter. The electron micrographs presented in this communication provide the best visual evidence yet that amyloids can form through the association of smaller structured bead-like intermediates. The results also suggest that folded beta-sheet-rich subunits can participate in amyloid formation.
authors.affiliation: Institute of Microbial Technology, Chandigarh 160036, India.
authors.forename: A
authors.initials: A
authors.lastname: Shukla
authors.forename: M
authors.initials: M
authors.lastname: Raje
authors.forename: P
authors.initials: P
authors.lastname: Guptasarma
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000378:metabolism; D011232:Chemical Precipitation; D019281:Dimerization; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D013696:Temperature
chemical_list: D000682:Amyloid; D029742:Caenorhabditis elegans Proteins; D006360:Heat-Shock Proteins; D046912:Multiprotein Complexes