title: Introduction of glutamines into the B2-H2 loop promotes prion protein conversion.
abstract: In prion diseases cellular prion protein (PrP(C)) undergoes conformational transition into the β-sheet-rich form (PrP(Sc)). PrP(C) consists of the disordered N-terminal part and a C-terminal globular domain containing three α-helices (H1, H2, H3) and an antiparallel beta sheet (B1, B2). B2-H2 loop, which has a focal role in the species barrier, contains the highest density of asparagine (N) and glutamine (Q) residues in the whole sequence. Q/N-rich domains are essential for the conversion of yeast prions. We investigated the role of Q/N residues in the B2-H2 loop in PrP conversion. We prepared mouse PrP mutants with increasing number of consecutive Q/N residues in the B2-H2 loop. Stability of the mutants decreased with the increasing number of inserted glutamines. In vitro conversion of mutants yielded fibrils of similar morphology as the wild-type PrP. Q/N mutants accelerated fibrillization in comparison to the wild-type PrP, with mutant containing the most glutamines having the shortest lag phase. The effect of Q/N residues was specific for the B2-H2 loop and was not due to simple increase in flexibility as the introduction of Gly-Ser or Ala residues slowed the conversion despite their decreased stability. Our results thus suggest that Q/N residues in the B2-H2 loop of PrP promote protein conversion and may represent a link to conversion of Q/N-rich prions.
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
authors.forename: Matevž
authors.initials: M
authors.lastname: Avbelj
authors.forename: Iva
authors.initials: I
authors.lastname: Hafner-Bratkovič
authors.forename: Roman
authors.initials: R
authors.lastname: Jerala
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D000818:Animals; D001216:Asparagine / Q000737:chemistry / Q000235:genetics; D005973:Glutamine / Q000737:chemistry* / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D018621:PrPC Proteins / Q000737:chemistry* / Q000235:genetics; D018620:PrPSc Proteins / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary
chemical_list: D000682:Amyloid; D018621:PrPC Proteins; D018620:PrPSc Proteins; D005973:Glutamine; D001216:Asparagine